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.rs
\v | 5i'
.LP
\fBMONTAGE : FIN DU \(sc 5.7 EN\(hyT\* | TE DE CETTE PAGE\fR 
.sp 2P
.LP
\v'23P'
\fB6\fR 	\fBAlgorithms for transmission planning\fR (from Ellemtel,
Sweden)
.RT
.sp 2P
.sp 1P
.RT
.PP
This Section compares loudness ratings calculated by algorithms as defined 
in the IEEE, the OREM\(hy8 and the Recommendation\ P.79 standards 
with P.79A, an adaptation of Recommendation\ P.79 for transmission planning. 
The computations encompassed 71\ different telephone set characteristics 
and 
27\ cases of subscriber cable attenuation distortions.
.PP
The results show that, in typical transmission planning situations,
the loudness ratings by\ P.79A are closely related to the others. In addition, 
P79A has the best additivity accuracy and the simplest form. Administrations 
are therefore urged to make some comparative studies using this P.79A
algorithm in transmission planning.
.RT
.sp 1P
.LP
6.1
	\fIIntroduction\fR 
.sp 9p
.RT
.PP
Some preliminary comparisons between different loudness loss
estimation methods for telephone network transmission planning are presented
(sidetone algorithms are not treated, however). The methods discussed are 
all based on objective measurements on telephone instruments. 
.PP
The transmission planner has some basic
requirements:
.RT
.LP
	1)
	to obtain a meaningful and reliable indication of the
telephone speech transmission quality as regards the
acoustic loss between the talking subscriber's mouth and the
listening subscriber's ear;
.LP
	2)
	to characterize the individual parts of a connection by
numerical values in such a way that their sum equals the
acoustic loss measure of the complete
connection;
.LP
	3)
	to ensure that the numerical values can be determined
reliably, inexpensively and with sufficient accuracy from
measurements.
.PP
The third requirement means that for quality control and
day\(hyto\(hyday use only \fIobjective\fR  | electro\(hyacoustic measurements 
can be 
considered. Of course, subjective measurements have been absolutely necessary 
in the past to establish the general level of reference. But they are more 
costly to carry out and give far less repeatable results even under favourable 
conditions. For example the CCITT Laboratory has periodically made subjective 
reference equivalence measurements on the same stable telephone set since 
late\ 1981. The values seem to wander slowly with time within a 3\ dB range.
See\ [12].
.bp
.sp 1P
.LP
6.2
	\fIDifferent\fR 
\fIloudness rating methods\fR 
.sp 9p
.RT
.PP
Objective electroacoustic loss (or sensitivity) measurements form the basis 
of several planning methods used by Administrations for their 
national
networks. The most important of these \*Qloudness ratings\*U are listed 
below, in the order most widely applied. 
.RT
.LP
	1)
	\fIIEEE standard\fR .\ This is now used in the USA and Canada. It
is well\(hydocumented and reliably instrumented (see \(sc\ 1
and\ [1]).
.LP
	2)
	\fIOREM\(hyB standard\fR  | (in different versions). The version
worth comparing to is currently being more accurately
redefined by a standardization body in the Federal Republic
of Germany.
.LP
	3)
	\fIReference equivalents\fR , but determined objectively by some
kind of instrumentation. It should be noted that the
\*Qreference loss\*U of a junction circuit is often determined
as the dB\ average over a log(f)\(hyscale.
.LP
	4)
	Recommendation P.79. This is the \*Qyoungest\*U standard. The
U.K. has the widest experience in its application. From a
transmission planner's point of view it leaves something to
be desired, and a possible modification is described
in\ [13].
.PP
Of course, to ensure telephone speech loudness quality in
international connections it is desirable that Administrations employ methods 
for loudness rating evaluations which are compatible, or preferably identical. 
The aim of this exposition is to show that for transmission planning a 
modified, or amended, version of Recommendation\ P.79 is compatible with the
IEEE, the OREM\(hyB and the original Rec.\ P.79 standard, as well as with
some aspects of the reference equivalent practice. In addition, this amended
P.79\ algorithm needs much less computation effort. (The principles are given
in\ [13] and in \(sc\ 5).
.PP
For a transmission planner the most important loudness parameters are the 
send, the receive and the junction loudness ratings. Note that the send 
and receive loudness ratings for transmission planning purposes \fIdo not\fR 
have to 
relate uniquely to subjective values determined by comparison with some
reference telephone system set\(hyup. The important aspect is that the
(send\ +\ receive\ +\ junction) loudness ratings add up to the correct overall
loudness rating (OLR), which in turn should have a good correlation with a
subjective measure. (But this cannot mean that different countries can use
different ratings that subdivide the OLR differently!)
.PP
What order of computation accuracy is needed? With regard to the
additivity of loudness ratings as well as for setting limits in a national
transmission plan, 0.5\ dB accuracy would probably be adequate. For translating 
between different standards, 1.5\ dB seems sufficient. (The loudness rating 
manufacturing tolerances for telephone sets, however, have to be much
wider).
.RT
.sp 1P
.LP
6.3
	\fIBasics of the loudness rating methods\fR 
.sp 9p
.RT
.PP
The physiological background to the loudness rating methods is as   follows:
.PP
The ear functions as a bank of narrow bandpass filters. (About
64\ equivalent filters having bandwidths of 50\(hy500\ Hz, called \*Qcritical
frequency bands\*U). In a specific band only, that portion of the sound energy
which lies above the hearing threshold is presented to the brain as a stimulus. 
The brain combines all filter outputs of a complex sound (such as the human 
voice) into an impression of loudness.
.PP
Each filter contributes in proportion to an exponent \fIm\fR  | of its
output power, \fIm\fR  | being in the order of 0.2\(hy0.3 for normal speech 
levels. 
For very low levels, near the threshold of hearing, as well as for very high
levels, \fIm\fR \ equals\ 1, corresponding to power addition. But it is 
important to note that for normal telephone speech, weaker spectral components 
contribute 
more to the total loudness impression than if they were added on a direct 
power basis. As a matter of fact, they approximately add on a linear 
dB\ scale.
.PP
A more complete theory of hearing, according to Zwicker, also takes
into account certain masking effects between the stimuli from the different
frequency bands. For telephone purposes, however, the Zwicker method does 
not seem to give any better agreement with subjective values. See\ [11] 
and\ [7].
.bp
.PP
In an active telephone connection the listener's impression of
loudness is influenced by his own hearing sensitivity/frequency curve and 
the talker's speech spectrum. A general loudness rating thus has to consider 
the 
statistical average for the human population.
.PP
The loudness rating algorithms mentioned can all be written in the
following form:
\v'6p'
.RT
.ad r
.ad b
.RT
.ad r
.ad b
.RT
.LP
where
\v'6p'
.ad r
.ad b
.RT
.LP
	 \fIL\fR\d0\u, \fIm\fR  | and \fIK\fR\d\fIi\fR\u | are constants. The 
index \*Q\fIi\fR \*U refers 
to the frequency\ \fIf\fR\d\fIi\fR\u.
.LP
	\fIL\fR\d\fIi\fR\u | is the appropriate measured and/or computed
electroacoustic loss in\ dB for send, receive, overall and junction
rating respectively.
.PP
The coefficients \fIK\fR\d\fIi\fR\u | depend on the \*Qaverage\*U speech and
hearing properties, some average transmission characteristics of a typical
circuit, as well as the spacing between the frequencies\ \fIf\fR\d\fIi\fR\u. 
Thus the \fIK\fR\d\fIi\fR\u's are in general frequency\(hydependent with 
proportionally lower 
values at the band edges. (An example of how to determine the \fIK\fR\d\fIi\fR\u's 
is found in\ [6]). However, the exact form of the \fIK\fR\d\fIi\fR\uvariation 
is not very critical, as will be shown in the following. 
.PP
A useful insight into the mathematical behaviour of the
loudness rating formula can be had from a Taylor series expansion.
Put
\v'6p'
.RT
.ad r
.ad b
.RT
.LP
Equation (6\(hy1b) can now be written as
\v'6p'
.ad r
.ad b
.RT
.LP
ignoring higher\(hyorder terms. Here
\v'6p'
.ad r
.ad b
.RT
.LP
The coefficient \fIa\fR  | is small, in the range 0.02 to 0.03 for \fIm\fR 
 | in the 
range 0.175 to\ 0.3.
.PP
Thus, the exact value of \fIm\fR  | is quite uncritical, as will be
shown numerically below. As a matter of fact, the second term in equation\ 
(6\(hy4) can be almost disregarded if the \fIL\fR\d\fIi\fR\u's deviate 
only moderately from the average\ \fIL\fR\d\fIm\fR\u, which is the case 
for most telephone send and 
receive characteristics.
.PP
This explains why send, receive and junction loudness ratings can
be added to get the overall loudness rating, at least as long as no hard
band\(hylimiting is included in the frequency range.
.PP
Moderate variations in the coefficients \fIK\fR\d\fIi\fR\u | between diferent
algorithms can of course be interpreted as small correction terms to be 
added to the \fIL\fR\d\fIi\fR\u's. Thus, the results from different algorithms 
can be 
expected to differ only by some constants, fairly independent of the telephone 
set characteristics. 
.bp
.PP
Similarly, other corrections involving small frequency\(hydependence can 
also be treated as constants added to the loudness ratings (for example 
earcap leakage, difference between measuring set\(hyups,\ etc.). 
.PP
In practice, the transmission bandwidth of a telephone connection may of 
course differ, depending on what type of links are included. Discussions 
of how this can be handled when determining the loudness rating can be 
found 
in\ [13] and in \(sc\ 5, which propose an amendment to Rec.\ P.79.
.PP
To investigate the properties of various loudness rating algorithms it 
is useful to make computations for a number of typical telephone set 
characteristics. Below, seventy\(hyone widely different characteristics 
have been used to obtain a statistical picture. See Annex\ B for details. 
.RT
.sp 1P
.LP
6.4
	\fIParticulars about some algorithms\fR 
.sp 9p
.RT
.PP
Only the mathematics of the algorithms are dealt with. Differences in the 
measuring arrangements are not considered here. The statistics refer to 
computations using the 71\ different set characteristics as mentioned above. 
The result of the computations are given with 0.01\ dB precision only to 
show the 
differences clearly. This \*Qaccuracy\*U is of course not at all necessary or
useful in practice.
.RT
.sp 1P
.LP
6.4.1
	\fIIEEE standard\fR 
.sp 9p
.RT
.PP
The computation range is 0.3 to 3.4 kHz with \fIm\fR \ =\ 0.22. The
\fIK\fR\d\fIi\fR\u\(hyweighting is flat on a log (
\fIf\fR )\(hyscale, i.e.\ all
\fIK\fR\d\fIi\fR\u's are
equal except the end points which have half the value. (From a physiological
point of view the weighting should really taper off slightly at the band
edges).
.PP
In the calculations presented here, 43 frequency points have been
used.
.RT
.sp 1P
.LP
6.4.2
	\fIOREM\(hyB standard\fR 
.sp 9p
.RT
.PP
Measurements of OREM values have traditionally been made with
special electroacoustic instruments. Recently, however, FTZ in the Federal
Republic of Germany has found it possible to compute OREM\(hyB values according 
to Equation\ (6\(hy1) using measured sensitivity curves\ [14]. 
.PP
The computation range is 0.2 to 4 kHz with \fIm\fR \ =\ 0.3. The
\fIK\fR\d\fIi\fR\u\(hyweighting is flat on a log (
\fIf\fR )\(hyscale as for the
IEEE method, but for
the send and overall loudness ratings the loss of a SFERT filter is added to
\fIL\fR\d\fIi\fR\uin Equation\ (6\(hy1). Fifty\(hythree frequency points 
are used. 
.RT
.sp 1P
.LP
6.4.3
	\fIRec. P.79 standard\fR 
.sp 9p
.RT
.PP
The computation range most often used is 0.2 to 4 kHz with
m\ =\ 0.175. The constants \fIL\fR\d0\uand \fIK\fR\d\fIi\fR\u | are transformed 
into the 
so\(hycalled \fIW\fR\d\fIi\fR\u\(hyweights which are added to the \fIL\fR\d\fIi\fR\u's. 
The 
earcap leakage \fIL\fR\d\fIE\fR\uis included for RLR and\ OLR.
.PP
The \fIW\fR\d\fIi\fR\u's are of course tabulated in Recommendation\ P.79 
and the corresponding \fIK\fR\d\fIi\fR\u's are shown in diagrams in\ [7]. 
Fourteen 
frequency points, spaced 1/3\ octave apart, are used.
.PP
The Rec. P.79 constants were tailored to make computed
loudness ratings agree with the correspondings subjective values obtained 
by a \fIspecific\fR CCITT test team some years ago. Therefore, in some 
respects 
Rec.\ P.79 does not quite represent subjective values obtained by
\*Qordinary\*U people. Rec.\ P.79 puts too much emphasis on the lower
frequencies and the weighting coefficients show some peculiar irregularities. 
(See\ [11] and\ [7] for a discussion.) Also, if a connection contains links 
of 
different bandwidths some ambiguity may occur.
.PP
When applying Rec. P.79 in practice, computer programs are
most often used. Telephone set sensitivity curves and chain matrix data 
of the individual links are the inputs, and SLR and RLR are computed to 
an interface terminated by 600\ ohms (which, incidentally, may not be the 
nominal impedance at that point!). JLR is not calculated very often. 
.bp
.RT
.sp 1P
.LP
6.4.4
	\fIAn amended Rec. P.79 standard: P.79A\fR 
.sp 9p
.RT
.PP
Details of this proposal are given in [13].
.PP
Eleven frequency points spaced 1/3 octave apart, are used. The
computation frequencies start at\ 0.315 and end at 3.15\ kHz, making the range
extend virtually from 0.3\ to 3.4\ kHz.
.PP
The \fIK\fR\d\fIi\fR\u's are all equal to 0.1 except for the end points
where they are equal to\ 0.05. This trapezoidal weighting thus takes some
account of the physiological facts about speech spectrum and hearing
sensitivity curves.
.PP
Loudness rating for tandem\(hyconnected links of wider bandwidths than
0.3\(hy3.4\ kHz is taken care of by the \*Qloudness\(hyimprovement\*U \fIE\fR 
\(hyfactor, which is subtracted from\ OLR. 
.PP
In the more \*Qexact\*U version of the amendment, \fIm\fR \ =\ 0.2. This 
is here designated \*QP.79A1\*U. 
.PP
A simpler approach is to let \fIm\fR \ =\ 0, i.e. use the weighted loss
average according to Equation\ (6\(hy3). This version is here designated
\*QP.79A\*U.
.PP
In Equation (6\(hy1) the constant \fIL\fR\d0\uis:
.RT
.LP
	for SLR:
	\(em\ 3
.LP
	for RLR:
	\ 12
.LP
	for OLR:
	\ \ 9
.LP
	for JLR:
	\ \ 0
.PP
When using P.79A1 or P.79A there is much less need for complex
computer programs. The LRs of the individual links can be added with good
accuracy.
.sp 1P
.LP
6.4.5
	\fIDependence on the m\(hyvalue\fR 
.sp 9p
.RT
.PP
The designation \*Q\fId\fR \*U is used to illustrate the change of a
loudness
rating as a function of the coefficient\ \fIm\fR . The \*Qnorm\*U value 
of a particular standard corresponds to \fId\fR \ =\ 0. 
.PP
It can be seen from Table 6\(hy1 that the choice of \fIm\fR  | is very
uncritical. It explains why P.79A1 with \fIm\fR \ =\ 0.2 and P.79A with 
\fIm\fR \ =\ 0 are 
fairly equivalent.
.RT
.LP
.sp 3
.ce
\fBH.T. [T19.19]\fR 
.ce
TABLE\ 6\(hy1
.ce
\fBValues of d (i.e. changes in LR) as a function of m\fR 
.ce

.ce
(Statistics from 71 telephone set characteristics)
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(42p) | cw(30p) | cw(42p) sw(36p) | cw(42p) sw(36p) , ^  | ^  | c | c | c | c.
Standard	m	Send	Receive
		Mean	Standard deviation	Mean	Standard deviation
_
.T&
lw(42p) | cw(30p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
IEEE	0.175	\(em0.15	0.05	\(em0.22	0.02
.T&
lw(42p) | cw(30p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
	0.2\ \ 	\(em0.05	0.02	\(em0.08	0.01
.T&
lw(42p) | cw(30p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
	0.22\ 	\fB\(em\fR 0\fB.05\fR	0\fB.02\fR	\fB\(em\fR 0\fB.08\fR	0\fB.01\fR
_
.T&
lw(42p) | cw(30p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
OREM\(hyB	0.175	\(em0.21	0.13	\(em0.22	0.11
.T&
lw(42p) | cw(30p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
	0.2\ \ 	\(em0.13	0.10	\(em0.14	0.08
.T&
lw(42p) | cw(30p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
	0.3\ \ 	\fB\(em\fR 0\fB.05\fR	0\fB.02\fR	\fB\(em\fR 0\fB.08\fR	0\fB.01\fR
_
.T&
lw(42p) | cw(30p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
P.79A1	0.02\ 	\fB\(em\fR 0.33	0.21	\fB\(em\fR 0.07	0.07
.T&
lw(42p) | cw(30p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
	0.175	\fB\(em\fR 0.05	0.03	\fB\(em\fR 0.01	0.01
.T&
lw(42p) | cw(30p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
	0.2\ \ 	\fB\(em\fR 0\fB.05\fR	0\fB.02\fR	\fB\(em\fR 0\fB.08\fR	0\fB.01\fR
_
.TE
.nr PS 9
.RT
.ad r
\fBTable 6\(hy1 [T19.19], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
6.4.6
	\fIAdditivity properties\fR 
.sp 9p
.RT
.PP
An indication of how well a certain algorithm is suited for
planning purposes is how closely the sum of send, junction and receive 
ratings corresponds to the overall rating. The difference between OLR and 
the sum of 
SLR\ +\ JLR\ +\ RLR is denoted as\ \*Q\fID\fR \*U.
.PP
Of special interest is how links of different bandwidths are treated. In 
a local, analog network the transmission range can be considered as 0.2\ 
to 4\ kHz. In a long\(hydistance network (including international links) 
one can 
hardly be assured of transmission outside the range 0.3\(hy3.4\ kHz.
Modern PCM systems, digital exchanges,\ etc., may have an effective band
of 0.2\(hy3.4\ kHz.
.PP
The IEEE standard only deals with the \*Qnarrow band\*U
0.3\(hy3.4\ kHz.
.PP
The amended P.79 standard (P.79A1 and P.79A) uses the same \*Qnarrow
band\*U for SLR, RLR and JLR calculations. If the actual transmission band is
wider, the sum is diminished by a \*Qloudness improvement factor\*U\ \fIE\fR 
to obtain an OLR which has a good correlation with subjective loudness 
impressions. 
(See\ [13] and \(sc\ 5.)
.PP
The unmodified P.79 standard for practical cases uses the range
0.2\(hy4\ kHz. Depending on the bandwidths of the links and the choice of
interface to which the SLR and RLR calculations refer, some ambiguity
can then occur.
.PP
In Table 6\(hy2 values of \fID\fR are given and, for reasons of simplicity, 
the junction is considered to have a flat frequency response over the frequency 
band considered. 
.PP
Note the large errors when P.79 is applied to a \*Qnarrow band\*U
connection such as can be expected in international calls.
.PP
The IEEE standard has the second worst additivity performance. (But it 
is of course satisfactory in practice.) 
.RT
.ce
\fBH.T. [T20.19]\fR 
.ce
TABLE\ 6\(hy2
.ce
\fBValues of  D = OLR\(hySLR\(hyRLR; JLR = 0\fR 
.ce
(Statistics from 71 telephone set characteristics)
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
Algorithm	Band (kHz)	D (mean)	Standard deviation	D (max.)	D (min.)  
_
.T&
lw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
IEEE	0.3\(hy3.4	0.84	0.24	1.42	\fB\(em\fR 0.08
.T&
lw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
OREM\(hyB	0.2\(hy4\fB.4\fR	0.19	0.24	0.62	\(em0.48
.T&
lw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
P.79	0.2\(hy4\fB.4\fR	\(em0.48\fB\(em\fR	0.19	\(em0.11\fB\(em\fR	\(em0.98
.T&
lw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
P.79	0.2\(hy3.4	\(em0.12\fB\(em\fR	0.13	0.17	\fB\(em\fR 0.56
.T&
lw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
P.79	0.3\(hy3.4\fR	\(em1.78\fB\(em\fR	0.09	\(em1.60\fB\(em\fR	\(em2.09
.T&
lw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
P.79A1	0.3\(hy3.4\fR	\(em0.06\fB\(em\fR	0.20	0.45\fR	\(em0.70
.T&
lw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
P.79A	0.3\(hy3.4\fR	0\fB.06\fR	0\fB.20\fR	0\fB.45\fR	 {
\fB\(em\fR
0\fB.70\fR
 }
_
.TE
.nr PS 9
.RT
.ad r
\fBTable 6\(hy2 [T20.19], p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
6.5
	 \fINumerical comparisons between loudness ratings of different\fR \fIstandards\fR 
.sp 1P
.RT
.sp 1P
.LP
6.5.1
	\fIP.79 algorithm\fR 
.sp 9p
.RT
.PP
From a transmission planner's point of view, the use of the simple loudness 
rating algorithm P.79A seems attractive. It is then of special 
interest to compare with results obtained when applying the \*Qnormal\*U
P.79\ algorithm.
.PP
Table 6\(hy3 shows the differences for SLR, RLR and OLR for connections 
having different bandwidths. (The frequency response is assumed to be flat 
within the passband, however.)
.bp
.RT
.ce
\fBH.T. [T21.19]\fR 
.ce
TABLE\ 6\(hy3
.ce
\fBValues of D = LR(P.79)\(hyLR(P.79A)\fR 
.ce
(Statistics from 71 telephone set characteristics)
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
LR	Band (kHz)	D (mean)	Standard deviation	D (max.)	D (min.)  
_
.T&
cw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
SLR	0.2\(hy4\fB.4\fR	\(em1.12	0.53	0.15	\(em2.61
.T&
cw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
	0.2\(hy3.4\fR	\(em0.93	0.55	0.32	\(em2.47
.T&
cw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
	0.3\(hy3.4\fR	\fB\(em\fR 1.0\ 	0.38	1.68	\(em0.03
_
.T&
cw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
RLR	0.2\(hy4\fB.4\fR	\(em0.65	0.46	0.43	\fB\(em\fR 1.95
.T&
cw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
	0.2\(hy3.4\fR	\(em0.46	0.47	0.61	\(em1.73
.T&
cw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
	0.3\(hy3.4\fR	\fB\(em\fR 1.52	0.31	2.06	\fB\(em\fR 0.55
_
.T&
cw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
OLR	0.2\(hy4\fB.4\fR	\(em0.85	0.69	0.58	\(em2.57
.T&
cw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
	0.2\(hy3.4\fR	\(em0.77	0.71	0.72	\(em2.54
.T&
cw(48p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) | cw(36p) .
	0.3\(hy3.4\fR	\fB\(em\fR 0.75	0.54	1.78	\(em0.59
_
.TE
.nr PS 9
.RT
.ad r
\fBTable 6\(hy3 [T21.19], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.sp 1
.PP
It can be seen from Table 6\(hy3 that the P.79 and the P.79A
algorithms are reasonably equal to each other, considering the bandwidth
ambiguity of the\ P.79. They seem to give the same numerical values (on the
average) for a connection having a slightly narrower effective band than
0.2\(hy3.4\ khz but broader than 0.3\(hy3.4\ kHz, i.e.\ a case often to 
be expected in practice. 
.PP
As mentioned earlier, the junction loudness rating, JLR is of less
importance when using P.79 in practice. As a matter of fact JLR (P.79) 
can give somewhat misleading results because of the band edge peculiarities 
of the 
algorithm as discussed earlier.
.PP
JLR values calculated by the P.79A1 and P.79A algorithms are more
useful to the network planner for several reasons. The additivity properties
are better, and some previous investigations indicate good agreement with
subjective measurements of loudness loss\ ([15]). (As a matter of fact the
Swedish Administration has used similar algorithms for 20\ years.)
.PP
The more \*Qcomplete\*U algorithm P.79A1 may be safely assumed to give 
the closest agreement with subjective measurements of\ JLR. For the transmission 
planner it is of interest to compare with:
.RT
.LP
	a)
	JLR results when using the still simpler algorithm
P.79A.
.LP
	b)
	Circuit losses as defined by the difference in relative
levels (=\ \fIL\fR\d1\u).
.PP
When the frequency response curve is flat all these quantities are of course 
identical. But typical unloaded subscriber cable introduces a high 
degree of attenuation distortion in the telephone channel. A number of
cases\ (27) have been investigated, including different cable diameters,\ d.c.
resistance (lengths) and terminations.
.PP
For these investigations the cable data were: capacitance 45\ nF/km;
diameters 0.4, 0.5 and 0.7\ mm; lengths corresponding to 300, 600 and 1200\ 
ohms d.c.\ resistance. The terminations were 600, 900\ ohms and a typical 
complex 
impedance (200\ ohms in series with a parallel combination 820\ ohms and
115\ nF).
.PP
The difference of JLR calculated using two algorithms is presented in Figure\ 
6\(hy1 as a function of the cable attenuation distortion, i.e.\ 
the
difference between the loss at 4\ kHz and the loss at 0.2\ kHz. (For the same
length of a cable, the complex impedance termination gives the largest
distortion. In practice, distortions larger than about 15\ dB should be 
avoided for various reasons.) 
.bp
.PP
As can be seen from Figure 6\(hy1 the P.79A algorithm is sufficiently
accurate to be used for JLR calculations, the differences being less than
0.3\ dB for a distortion up to 15\ dB.
.RT
.LP
.rs
.sp 17P
.ad r
\fBFigure 6\(hy1, p.\fR 
.sp 1P
.RT
.ad b
.RT
.PP
The subscriber cable loss as defined by \fIL\fR\d1\u, the difference in 
relative levels, is simply the (composite) loss at 1\ kHz according to 
the CCITT definition (even for a complex impedance termination). Figure\ 
6\(hy2 shows that 
the difference to the \*Qtrue\*U JLR value is always less than 1\ dB, and 
presumably less than 0.5\ dB in the majority of practical cases. 
.PP
Thus the difference in relative levels, \fIL\fR\d1\u, can also be used,
with good accuracy, as a measure of the change in loudness rating,\ JLR. This
makes the task easier for the network planner.
.RT
.LP
.rs
.sp 19P
.ad r
\fBFigure 6\(hy2, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
6.5.2
	\fIIEEE and OREM\(hyB algorithms\fR 
.sp 9p
.RT
.PP
To what degree will it be possible to make simple conversions
between P.79A and the IEEE and OREM\(hyB standards? That is, what is the
difference
\v'6p'
.RT
.ce 1000
\fID\fR = \fILR\fR \(em \fILR\fR (P.79A) ?
.ce 0
.ad r
(6\(hy6)
.ad b
.RT
.LP
.sp 1
.PP
Of interest are the average \fID\fR (mean) and the standard
deviation for typical telephone set characteristics. Because possible
differences in measuring set\(hyups have not yet been investigated, it 
is for the moment only relevant to study the standard deviations. 
.PP
The computation results are presented in Table 6\(hy4. The standard
deviations are quite small, indicating that it will indeed be feasible 
to make simple conversions. 
.RT
.LP
.sp 3
.ce
\fBH.T. [T22.19]\fR 
.ce
TABLE\ 6\(hy4
.ce
\fBStandard deviation of [LR\(hyLR(P.79A)]\fR 
.ce
(Statistics from 71 telephone set characteristics)
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
Standard	LR	Band (kHz)	Standard deviation  
_
.T&
lw(54p) | lw(42p) | cw(42p) | cw(42p) .
IEEE	Send	0.3\(hy3.4	0.31
.T&
lw(54p) | lw(42p) | cw(42p) | cw(42p) .
	Receive		0.1\ 
.T&
lw(54p) | lw(42p) | cw(42p) | cw(42p) .
	Overall		0.4\ 
_
.T&
lw(54p) | lw(42p) | cw(42p) | cw(42p) .
OREM\(hyB	Send	0.2\(hy4\fB.4\fR	0.52
.T&
lw(54p) | lw(42p) | cw(42p) | cw(42p) .
	Receive		0.38
.T&
lw(54p) | lw(42p) | cw(42p) | cw(42p) .
	Overall		0.5\ 
_
.TE
.nr PS 9
.RT
.ad r
\fBTable 6\(hy4 [T22.19], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.sp 3
.sp 1P
.LP
6.6
	\fIConclusions\fR 
.sp 9p
.RT
.PP
A proposed amendment, P.79A, to the loudness rating
Recommendation\ P.79 has been investigated and found adequate for transmission 
planning purposes. (The algorithm\ P.79A corresponds in principle to taking 
a 
weighted dB\ average over a log (
\fIf\fR )\(hyscale. See \(sc\ 6.4.4 and\ [13].
.PP
The algorithm P.79A has been shown to give, with sufficient accuracy, numerically 
equal values with P.79 in typical transmission planning situations. P.79A 
can be expected, for good reasons, to agree better with subjective values 
than\ P.79. 
.PP
It also seems possible to make simple conversions between P.79A, IEEE and 
OREM\(hyB loudness ratings. 
.PP
P.79A has the best additivity accuracy as well as the most simple
form.
.PP
Administrations are therefore urged to make some comparative studies using 
this P.79A algorithm in transmission planning. 
.bp
.RT
.sp 2P
.LP
\fB7\fR 	\fBInformation on the Zwicker loudness rating method as used by
the French Administration\fR (Contribution from the French Administration)
.sp 1P
.RT
.sp 1P
.LP
7.1
	\fIIntroduction\fR 
.sp 9p
.RT
.PP
The method recommended for the evaluation of the quality of a
communication in terms of loudness is that of loudness rating (LR). The
subjective determination of these equivalents is described in
Recommendation\ P.78, and the objective determination in
Recommendation\ P.79.
.PP
However, other parameters (e.g. R25E) have been used, and no universal 
formula is available to transform these parameters into\ LR. Therefore 
it will be useful to have a description of how both values (e.g.\ R25E 
and\ LR) can be 
objectively measured for a given equipment.
.PP
This Section sets out to describe a method for an objective evaluation 
of loudness losses (R25 equivalents and loudness ratings) used by the French 
Administration, as stated in the SG\ XII/3\ Report, in Boglarlelle, May\ 1987
(TD64\ revised).
.RT
.sp 1P
.LP
7.2
	\fICharacteristics of the method\fR 
.sp 9p
.RT
.PP
The computation of the loudness of stationary\(hytype signals using
the Zwicker algorithm, when applied to the objective measurement of
R25\ equivalents and\ LR, gives results which are in good agreement with
results obtained using the corresponding subjective evaluation
methods\ [16].
.PP
One specific characteristic of this algorithm is that it can be used to 
compare loudness between systems whose transmitted frequency bandwidth 
is 
not within the limits of 300\(hy3400\ Hz.
.PP
Adaptations of the Zwicker algorithm to monaural and binaural
listening modes respectively are used to evaluate different types of terminals: 
handset telephones\ [16], operator headsets\ [17] and loudspeaker 
telephones\ [18].
.PP
It is essential to use \*Qcomplex\*U voices as defined in
Recommendation\ P.51 to measure nonlinear systems. This algorithm has lead to
satisfactory results in the evaluation of hand\(hyfree sets\ [19] when 
using such input voices. 
.RT
.sp 1P
.LP
7.3
	\fIPrinciple of Zwicker's algorithm to calculate loudness\fR 
.sp 9p
.RT
.PP
The method is based on the use of method B of ISO 532
Rec. (Zwicker method).
.RT
.sp 1P
.LP
7.3.1
	\fIEssential phenomena considered in the\fR 
\fIcalculation of\fR 
\fIloudness\fR 
.sp 9p
.RT
.PP
The algorithm establishes a relationship between the stimulus
(physical) and the auditory sensation (psychoacoustical). Loudness is composed 
of three main phenomena which are as follows: critical bands, masking and 
equal loudness levels. 
.RT
.sp 1P
.LP
7.3.1.1
	\fICritical bands\fR 
.sp 9p
.RT
.PP
In the human ear, wideband sounds seem to be louder than pure or
narrow\(hyband sounds with the same acoustic pressure levels. It is also 
possible to prove that, around a given frequency and for a fixed level 
of acoustic 
pressure, loudness remains constant as long as the sound bandwidth does not
exceed a given value called the critical band. If sound bandwidth exceeds 
this value, a distinct increase in loudness can be noted. In this way, 
the ear 
divides the domain of audible frequencies into 24\ critical bands, within 
which any excitation is integrated without weighting. Therefore, loudness 
measurement is based upon spectral sound analysis. 
.RT
.sp 1P
.LP
7.3.1.2
	\fIMasking effect\fR 
.sp 9p
.RT
.PP
The masking effect consists of raising a (reference) sound's
threshold level of audibility when transmitting another sound of a (masking)
noise with a lower frequency (or higher, but in a weaker proportion). This 
can be explained via the notion of specific loudness. 
.RT
.sp 1P
.LP
7.3.1.2.1
	\fISpecific loudness\fR 
.sp 9p
.RT
.PP
A narrow band of noise or a pure sound, whose spectral energy is
concentrated at one specific point of the frequency range, causes a large
portion of the basilar membrane (one of the essential auditory organs) to
vibrate. This causes not only an excitation of the centre, but also an
excitation of the sides which is especially significant in frequency zones
above that of the signal frequency. The effect of these side excitations 
shows itself via the masking effect. The excitations of the centre and 
the sides 
contributes to the specific signal loudness.
.bp
.RT
.sp 1P
.LP
7.3.1.2.2
	\fIMasked or partially masked loudness\fR 
.sp 9p
.RT
.PP
If a weak sound falls in the highest frequency zone as defined
above, it can be masked partially or totally by the side excitations, and
therefore does not produce any specific loudness.
.RT
.sp 1P
.LP
7.3.1.3
	\fIEqual loudness levels\fR 
.sp 9p
.RT
.PP
The ear is not equally sensitive to different frequencies; curves of equal 
loudness levels allow to compare the loudness of sounds produced by 
sounds of different frequencies once the signal levels have been physically
measured. On an \*Qacoustic pressure level vs. frequency\*U diagram, these 
curves link the points which correspond to an equal sensation of sound 
loudness, 
including those found at the threshold of hearing.
.RT
.sp 1P
.LP
7.3.2
	\fIGlobal loudness of a complex sound\fR 
.sp 9p
.RT
.PP
Using a spectral analysis in thirds of octaves
.FS
Third octave
bands are a good approximation of the critical bands, provided that bands 
lower than 280\ Hz are appropriately grouped together. 
.FE
the Zwicker method\ [20] is used to calculate the loudness of stationary 
signals with the following double correction: 
.RT
.LP
	\(em
	 by transforming the pressure level in each third octave band into a specific 
loudness, 
.LP
	\(em
	by a specific loudness summation, weighted by the masking
effect.
.sp 1P
.LP
7.3.3
	\fIComputer measurement of loudness\fR 
.sp 9p
.RT
.PP
This measurement is possible since the acoustic pressure level for each 
third octave band is known. The FORTRAN program enabling this loudness 
to be computed is described in\ [21]. 
.PP
\fINote\fR \ \(em\ The Zwicker algorithm includes two variants: one for
listening in a free field, the second for listening in a diffuse field.
Results referenced in\ [16], [17] made use of the first variant. Both lead
to satisfactory values when applied for the determination of\ R25
and\ LR.
.RT
.sp 2P
.LP
7.4
	 \fIApplication of the Zwicker method for measuring the loudness\fR \fIloss 
(LL): R25 equivalents (R25E) and loudness ratings (LR)\fR 
.sp 1P
.RT
.sp 1P
.LP
7.4.1
	\fIFundamental principle of the objective LL measuring method\fR 
.sp 9p
.RT
.PP
The principles on which the following instrumental method are based are 
similar to the subjective methods described in Figures\ 7\(hy1 and\ 7\(hy2 
for 
determining the R25\ equivalents and\ LR. In this method:
.RT
.LP
	a)
	The speech signals are replaced by an artificial acoustic
voice, the spectral characteristics of which are given in
Recommendation\ P.51.
.LP
	b)
	The reference parameters and signals are calculated on the
basis of the nominal efficiency characteristics, as a
function of the frequency of the NOSFER and IRS defined
in\ P.42 \fI(Red Book)\fR and\ P.48. These are:
.LP
	\(em
	the artificial electric voices resulting from the
transmission of acoustic artificial voice via reference
transmission systems,
.LP
	\(em
	the NOSFER reference loudness\ (RL),
.LP
	\(em
	the loss \fIx\fR\d2\uas a result of comparing
and equalizing the loudness of NOSFER and
IRS\ paths.
.LP
	c)
	 The values of \*Q\fILE\fR \*U relative to acoustic leakage are used as 
artificial ear/real ear correcting terms. 
.LP
	d)
	Operator evaluation of sound loudness is replaced by
a calculation of the loudness of stationary noise intercepted by a
standardized artificial ear, and is performed according to Zwicker's
algorithm.
.LP
.sp 1
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 7\(hy1, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 7\(hy2, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
7.4.2
	\fICharacteristics of reference signals and parameters\fR 
.sp 9p
.RT
.PP
The reference signals and parameters which objectively characterize speech 
communication in Figures\ 7\(hy1 and\ 7\(hy2 are defined hereafter. 
.PP
\fINote\fR \ \(em\ Whether it is a question of human or artificial mouths and
ears, the definition of mouth and ear reference points (MRP and ERP) does 
not change (Annex\ A of Recommendation\ P.64) and the standardized speaking 
positions are identical. 
.RT
.LP
	\(em
	 \fIAcoustic artificial voice:\fR \ defined at the MRP. For spectral characteristics, 
see Table\ 2/P.51. 
.LP
	\(em
	 \fIElectrical artificial voices:\fR \ these voices substitute, at points 
JS in Figures\ 7\(hy1 and 7\(hy2, for the human voice/NOSFER or IRS\ systems. 
For spectral characteristics see Tables\ 7\(hy1 and\ 7\(hy2 (columns\ \fIN\fR\d\fIT\fR\u 
and\ \fIN\fR\d\fIS\fR\urespectively).
.LP
	\(em
	 \fIReference loudness\fR \fI(RL):\fR \ loudness of the acoustic signal 
at the e.r.p. of \*Qpath\ 0\*U, when the acoustic artificial voice is applied 
to the\ MRP. 
\v'6p'
.sp 1P
.ce 1000
RL = 21.1 sones
.ce 0
.sp 1P
.LP
.sp 1
	\(em
	 \fIx\fR\d2\u:\ loss calculated according to the flowchart in Figure\ 
7\(hy4 to give equal loudness for paths\ 0 and\ 2 (Figure\ 7\(hy2). 
\v'6p'
.sp 1P
.ce 1000
\fIx\fR\d2\u= 21.5 dB
.ce 0
.sp 1P
.LP
.sp 1
.LP
	\(em
	\fIAcoustic leakage\fR \fI\*QLE\*U:\fR \ defined in two
cases:
.LP
	i)
	for the telephone set receiver
(Table\ 4/P.79)
.LP
	ii)
	for the NOSFER receiver (Table\ 7\(hy3,
\fILE\fI\d\fIR\fR\u).
.LP
.sp 5
.ce
\fBH.T. [T23.19]\fR 
.ce
TABLE\ 7\(hy1
.ce
\fBElectrical artificial voice of the NOSFER\fR 
.ce
(output of the NOSFER sending system)
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
Frequency (Hz)	\fIN\fI  (dBV)	Frequency (Hz)	\fIN\fI  (dBV)  
_
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
100	\(em29.7	1000	\(em20.3
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
125	\(em24.7	1250	\(em22.1
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
160	\(em21.4	1600	\(em24.3
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
200	\(em19.2	2000	\(em26.0
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
250	\(em18.6	2500	\(em27.8
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
315	\(em18.4	3150	\(em28.1
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
400	\(em18.7	4000	\(em29.9
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
500	\(em18.7	5000	\(em34.8
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
630	\(em18.8	6300	\(em42.7
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
800	\(em19.4	8000	\(em46.4
_
.TE
.nr PS 9
.RT
.ad r
\fBTable 7\(hy1 [T23.19], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T24.19]\fR 
.ce
TABLE\ 7\(hy2
.ce
\fBElectrical artificial voice of the IRS\fR 
.ce
(output of the IRS sending system)
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
Frequency (Hz)	\fIN\fI  (dBV)	Frequency (Hz)	\fIN\fI  (dBV)  
_
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
100	\(em68.9	1000	\(em22.6
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
125	\(em55.3	1250	\(em23.3
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
160	\(em42.0	1600	\(em23.6
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
200	\(em33.6	2000	\(em24.8
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
250	\(em27.7	2500	\(em25.1
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
315	\(em23.8	3150	\(em26.8
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
400	\(em21.7	4000	\(em67.0
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
500	\(em21.0	5000	\(em82.8
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
630	\(em21.5	6300	\(em104.5\ 
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
800	\(em21.9	8000	\(em120.5\ 
_
.TE
.nr PS 9
.RT
.ad r
\fBTable 7\(hy2 [T24.19], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.sp 3
.ce
\fBH.T. [T25.19]\fR 
.ce
TABLE\ 7\(hy3
.ce
\fBNOSFER receiver acoustical leakage\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
Frequency (Hz)	\fILE\fI  (dB)	Frequency (Hz)	\fILE\fI  (dB)  
_
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
100	\fB\(em\fR 0.9	1000	\(em4.5
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
125	\fB\(em\fR 0.2	1250	\(em3.9
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
160	\(em0.6	1600	\(em4.6
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
200	\(em1.6	2000	\(em3.3
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
250	\(em2.9	2500	\(em3.2
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
315	\(em4.2	3150	\(em3.3
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
400	\(em5.3	4000	\(em3.7
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
500	\(em5.4	5000	\(em2.9
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
630	\(em4.9	6300	\(em0.8
.T&
cw(42p) | cw(42p) | cw(42p) | cw(42p) .
800	\(em4.6	8000	\(em0.8
_
.TE
.nr PS 9
.RT
.ad r
\fBTable 7\(hy3 [T25.19], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.sp 3
.sp 1P
.LP
7.4.3
	\fILoudness loss computation\fR 
.sp 9p
.RT
.PP
Generally, the measurement consists in comparing and setting the
reference loudness (RL) equal to the loudness of the various paths being
studied (Figures\ 7\(hy1 and\ 7\(hy2). However, considering the structural 
modification of these paths (see \(sc\ 7.4.2), the analogy between the 
subjective and the 
objective method is only possible if the signals which characterize these 
paths have been corrected (\(*b\fI\fI\d\fIi\fR\uterms of Figures\ 7\(hy3 
and\ 7\(hy4: acoustical leakage, nominal sensitivity/frequency of the reference 
receiving systems) before 
calculating their loudness and comparing them to the reference.
.PP
The R25 equivalents and LR are therefore calculated according to the flowcharts 
in Figures\ 7\(hy3 and\ 7\(hy4. 
.bp
.RT
.LP
.rs
.sp 47P
.ad r
\fBFigure 7\(hy3, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 7\(hy4, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
7.5
	\fIGeneral structure of the CERF apparatus\fR \fIof the French\fR 
\fIAdministration\fR 
.sp 9p
.RT
.PP
The diagram in Figure 7\(hy5 shows how the main elements of the
measuring device performing the operation described above are organized.
[22]\ gives a detailed description of the functions and features of the
device.
.RT
.LP
.rs
.sp 28P
.ad r
\fBFigure 7\(hy5, p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB8\fR \fBInformation on the OREM\(hyB loudness loss method\fR \fBas used 
by the Administration of the Federal Republic of Germany\fR (Contribution 
by the 
Administration of the Federal Republic of Germany)
.sp 1P
.RT
.sp 1P
.LP
8.1
	\fIDefinition\fR 
.sp 9p
.RT
.PP
Within the area of the Deutsche Bundespost, measurements of
loudness ratings are performed according to DIN\ 44013 \*QObjective
Reference Equivalent Measuring Device OREM\(hyB, Configuration and
Application.\*U
.RT
.sp 1P
.LP
8.1.1
	\fIOREM\(hyB loudness related ratings, BD\fR 
.sp 9p
.RT
.PP
By definition, the loudness BD is zero if a sound pressure of
1.6\ Pa is reached at the SFERT microphone in the Braun ear at a sound
pressure of 1.07\ Pa under the measurement conditions specified in
DIN\ 44013.
.RT
.sp 1P
.LP
8.1.2
	\fIOREM\(hyB send loudness, SBD\fR 
.sp 9p
.RT
.PP
The send loudness determined by operating the test item (e.g.\ a
telephone set together with the feeding bridge, possibly also with connected
lines and other equipment) as an electric transmitter and by comparing the
voltage measured at a 600\ ohm terminating impedance with the reference
voltage.
.bp
.PP
By definition, the \*QSBD\*U is zero if the output voltage at the SFERT
microphone in the presence of a 1.07\ Pa sound pressure is 285\ mV (see
Figure\ 8\(hy1).
.RT
.LP
.rs
.sp 24P
.ad r
\fBFigure 8\(hy1, p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
8.1.3
	\fIOREM\(hyB receive loudness, EBD\fR 
.sp 9p
.RT
.PP
The receive loudness determined by operating the test item (e.g.\ a telephone 
set together with the feeding bridge, possibly also with connected 
lines and other equipment) as an electric receiver and by comparing the 
sound pressure measured in the Braun ear with the reference sound pressure. 
.PP
By definition, the \*QEBD\*U is zero if the sound pressure measured at 
an open\(hycircuit voltage of the transmitter of 570\ mV (internal resistance: 
600\ ohms) is 1.6\ Pa (see Figure\ 8\(hy1).
.RT
.sp 1P
.LP
8.1.4
	\fIOREM\(hyB overall loudness, OBD\fR 
.sp 9p
.RT
.PP
(Overall loudness (OBD) of a telephone connection): The reference equivalent 
determined by comparing a complete telephone connection, possibily together 
with interposed lines and other equipment, with the OREM\(hyB reference 
transmitter and receiver (see Figure\ 8\(hy1). 
.RT
.sp 1P
.LP
8.1.5
	\fIOREM\(hyB sidetone loudness, RBD\fR 
.sp 9p
.RT
.PP
The sidetone loudness determined by comparing \(em in transmissions
from the microphone to the receiver capsule of the same test item (e.g.\ a
telephone set with a specific terminating impedance) the sound pressure 
of the receiver with the reference sound pressure. 
.PP
By definition, it is zero if the sound pressure measured in the Braun ear 
is 1.6\ Pa in the presence of a sound pressure of 1.07\ Pa at the SFERT 
microphone.
.bp
.RT
.sp 1P
.LP
8.2
	\fIMeasurement conditions deviating from Rec. P.64\fR \v'2p'
.sp 9p
.RT
.LP
	\(em
	Instead of the handset position according to Annex A of
Rec.\ P.76 [the loudness rating guard\(hyring position (LRGP)], a
position according to Rec.\ P.72 [reference equivalent speaking
position (RESP) \fI(Red Book)\fR ] is used.
.LP
	\(em
	Instead of the IEC coupler, a Braun coupler is used.
.LP
	\(em
	Use is made of an artificial mouth according to
Rec.\ P.51.
.LP
	\(em
	Calibration of the artificial mouth is not performed under
free\(hyfield conditions but with the aid of the SFERT baffle. The sound 
pressure build\(hyup in the SFERT baffle is compensated by an adequate 
filter in the 
generator section. At the diaphragm of the microphone in the SFERT baffle
(see Figure\ 8\(hy2), spaced 43.5\ mm apart from the lip plane, the sound 
pressure is 
set to 1.07\ Pa (sound pressure level: 94.6\ dB). Between 200\ Hz and 4000\ 
Hz, the sound pressure should be as frequency\(hyindependent as possible. 
In the process, the SFERT filter is activated. 
.LP
	\(em
	 Via a regulation loop, the sound pressure is kept constant at the calibration 
value (independently of the test item). 
.LP
.rs
.sp 21P
.ad r
\fBFigure 8\(hy2, p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
8.3
	\fIAlgorithm\fR 
.sp 9p
.RT
.PP
The successive voltages \fIU\fR\d1\u, \fIU\fR\d2\u. |  |  \fIU\fR\d\fIn\fR\u |
of the swept sinusoidal signal are added according to the following
law:
\v'6p'
.RT
.ad r
.ad b
.RT
.LP
for \fIt\fR\d\fIi\fR\u | approching 0:
\v'6p'
.ad r
.ad b
.RT
.LP
The exponent \fIm\fR  | is 0.6.
.LP
The static transient time of the indicator is 3.5\ s.
.LP
The frequency sweep 200 . |  |  4000 . |  |  200\ Hz is logarithmic with 
time, with a complete sweep cycle per second. 
.bp
.ce 1000
ANNEX\ A
.ce 0
.sp 1P
.ce 1000
(to Supplement 19 \(em ref. to \(sc\ 5.3)
.sp 9p
.RT
.ce 0
.sp 1P
.ce 1000
\fBE\(hyfactor coefficients\fR 
.sp 1P
.RT
.ce 0
.sp 1P
.PP
The attenuation values \fIL\fR\d\fIi\fR\u | are given for the \*Qwideband\*U
\fIf\fR\d1\u\ . |  | \ \fIf\fR\d\fIN\fR\u. The \*Qwideband\*U \fILR\fR 
(\fIW\fR ) is computed using the 
algorithm:
\v'6p'
.sp 1P
.RT
.ad r
.ad b
.RT
.PP
For shortness we use the notation:
\v'6p'
.ad r
.ad b
.RT
.PP
The \*Qcommon\*U band LR is computed in the narrower range:
\v'6p'
.ad r
.ad b
.RT
.PP
According to the definition of the \fIK\fR\d\fIi\fR\u\(hycoefficients we 
have: 
\v'6p'
.ad r
.ad b
.RT
.PP
The relationship between the two algorithms is defined to be as
follows:
.PP
For a strictly band\(hylimited system, i.e. one for which
\fIL\fR\d1\u\ . |  | \ \fIL\fR\d\fIN\fR\\d1\u\ =\ \(if, we let:
\v'6p'
.RT
.ad r
.ad b
.RT
.LP
and further we set:
\v'6p'
.ad r
.ad b
.RT
.LP
Thus, we get:
\v'6p'
.ad r
.ad b
.RT
.LP
and
\v'6p'
.ad r
.ad b
.RT
.LP
.bp
.PP
We will use the following notation:
\v'6p'
.ad r
.ad b
.RT
.PP
In the general case we have:
\v'6p'
.ad r
.ad b
.RT
.LP
which results in
\v'6p'
.ad r
.ad b
.RT
.PP
As the terms in the sum \(*s"
` in Equation (A\(hy11) are small,
one can make a series expansion. Thus:
\v'6p'
.ad r
.ad b
.RT
.LP
where
\v'6p'
.ad r
.ad b
.RT
.PP
The last term in Equation (A\(hy12) is designated as the loudness
improvement, the \fIE\fR \(hyfactor.
\v'6p'
.ad r
.ad b
.RT
.PP
In the actual case the \*Qwideband\*U can be taken to encompass the
range \fIf\fR\d1\u\ =\ 200\ Hz to \fIf\fR\d1\\d4\u\ =\ 4000\ Hz and the 
\*Qcommon\*U band 
\fIf\fR\d3\u\ =\ 315\ Hz to \fIf\fR\d1\\d3\u\ =\ 3150\ Hz. The \*Qband 
edge\*U frequencies are 200, 250\ and 4000\ Hz. 
.PP
The coefficients \fIC\fR\d\fIi\fR\u | have been computed for some LR algorithms
under discussion using the \fIK\fR\d\fIi\fR\u\(hyvalues for OLR as given 
in Table\ A\(hy1. (Details of the algorithms are given in\ [11] and\ [7] 
as well as the method used for converting \fIW\fR\d\fIi\fR\u\(hyweights 
to \fIK\fR\d\fIi\fR\u\(hyweights.) The 
\fIC\fR\d\fIi\fR\u\(hyvalues are presented in Table\ A\(hy2.
.RT
.PP
The P.79 algorithm or its smoothed version P.79/S are not suitable for 
band edge performance, analysis as their frequency weighting has been shown 
to be less correct (too much emphasis on the lower frequencies\ [7].) 
.PP
It is apparent from Table A\(hy2 that the \fIC\fR\d\fIi\fR\u\(hycoefficients 
from the three algorithms do not differ very much. As the human speech 
and hearing characteristics at the band edges can be expected to vary rather 
much, the 
actual values of the \fIC\fR\d\fIi\fR\u's cannot be critical. Therefore, it is
reasonable to use the \*Qrounded\(hyoff\*U values:
\v'6p'
.RT
.ad r
.ad b
.RT
.LP
and to set \fIm\fR \ =\ 0.2.
.bp
.PP
Which algorithm should be used when computing the
\*Qcommon\*U\(hyband\ LR? As shown in\ [11] and\ [7], there are several 
algorithms which correlate about equally well with subjective measurements. 
The simplest one is the algorithm\ \*Q\fIC\fR \*U which was therefore chosen. 
.LP
.sp 5
.ce
\fBH.T. [T26.19]\fR 
.ce
TABLE\ A\(hy1
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(48p) | cw(42p) sw(48p) sw(42p) , ^  | ^  | c | c | c.
Algorithm	m	\fIK\fI  
		0.2 kHz	0.25 kHz	4 kHz
_
.T&
lw(48p) | cw(48p) | cw(42p) | cw(48p) | cw(42p) .
P.XXE	0.225	0.0227	0.0389	0.0292
.T&
lw(48p) | cw(48p) | cw(42p) | cw(48p) | cw(42p) .
CH	0.2\ \ 	0.0306	0.0439	0.0324
.T&
lw(48p) | cw(48p) | cw(42p) | cw(48p) | cw(42p) .
B	0.2\ \ 	0.031\ 	0.042\ 	0.042\ 
.T&
lw(48p) | cw(48p) | cw(42p) | cw(48p) | cw(42p) .
P.79/S	0.175	0.0536	0.0765	0.0243
_
.TE
.nr PS 9
.RT
.ad r
\fBTable A\(hy1 [T26.19], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.sp 5
.ce
\fBH.T. [T27.19]\fR 
.ce
TABLE\ A\(hy2
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(48p) sw(42p) sw(48p) | cw(42p) , ^  | c | c | c | ^ .
Algorithm	\fIC\fI	 {
@  int  @
\fIC\fI
 }
	0.2 kHz	0.25 kHz	4 kHz
_
.T&
lw(48p) | cw(48p) | cw(42p) | cw(48p) | cw(42p) .
P.XXE	0.48	0.83	0.62	1.93
.T&
lw(48p) | cw(48p) | cw(42p) | cw(48p) | cw(42p) .
CH	0.74	1.06	0.79	2.59
.T&
lw(48p) | cw(48p) | cw(42p) | cw(48p) | cw(42p) .
B	0.76	1.03	1.03	2.82
.T&
lw(48p) | cw(48p) | cw(42p) | cw(48p) | cw(42p) .
Mean	0.66	0.97	0.81	2.45
_
.TE
.nr PS 9
.RT
.ad r
\fBTable A\(hy2 [T27.19], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 6P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.ce 1000
ANNEX\ B
.ce 0
.sp 1P
.ce 1000
(to Supplement 19 \(em ref. to \(sc\ 6.3)
.sp 9p
.RT
.ce 0
.sp 1P
.PP
Seventy\(hyone telephone set characteristics were obtained of
which:
.sp 1P
.RT
.LP
	a)
	thirteen from CCITT COM XII\(hyNo.\ 164 (1977\(hy1980), and
.LP
	b)
	fifty\(hyeight from Barnes in a private
communication.
.PP
The statistics of the send and receive sensitivity curves are
shown in Figures\ B\(hy1 and\ B\(hy2. The curves were normalized by subtracting 
the 
\*Qaverage\*U sensitivity computed by Equation\ (6\(hy1b).
.LP
.rs
.sp 18P
.ad r
\fBFigure B\(hy1, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 18P
.ad r
\fBFigure B\(hy1, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
	\fBReferences\fR 
.sp 1P
.RT
.LP
[1]
	IEEE Standard 661\(hy1979, \fIStandard method for determining objective\fR 
\fIloudness ratings of telephone connections\fR , \fIIEEE\fR , New York.
.LP
[2]
	CCITT Draft Recommendation P.XXE, Question 15/XII, Annex 2 (II)
Contribution COM\ XII\(hyNo.\ 1, Study Period\ 1977\(hy1980,
Geneva,\ 1976
.LP
[3]
	CCITT Contribution COM XII\(hyNo. 160, \fIUse of Zwicker's method for\fR 
\fIcomputing loudness ratings\fR (Australia), Study Period\ 1981\(hy1984,
Geneva,\ 1983.
.LP
[4]
	BARNES (J.): Private Communication, STL.
.LP
[5]
	CCITT Contribution COM XII\(hyNo. 10 (People's Republic of China), Study
Period\ 1981\(hy1984.
.LP
[6]
	CCITT Contribution COM XII\(hyNo. 55 (ELLEMTEL),
Study Period\ 1981\(hy1984.
.LP
[7]
	CCITT Contribution COM XII\(hyNo. 194 (ELLEMTEL),
Study Period\ 1981\(hy1984.
.LP
[8]
	 CCITT Contribution COM XII\(hyNo. 98, \fICalculation of loudness ratings 
for\fR \fIdifferent bandwidths\fR (British Telecom), Study Period\ 1981\(hy1984, 
Geneva,\ 1982.
.LP
[9]
	CCITT Contribution COM XII\(hyNo. 78, \fIAdditivity of loudness ratings\fR 
(ELLEMTEL), Study Period\ 1981\(hy1984, Geneva,\ 1982.
.LP
[10]
	CCITT Contribution COM XII\(hyNo. 111, \fIChoice of representative\fR 
\fIloss/frequency characteristics for electrical elements\fR (ITT/STL),
Study Period\ 1981\(hy1984, Geneva,\ 1983.
.LP
[11]
	CCITT Contribution COM XII\(hyNo. 176, \fILoudness rating algorithms\fR 
\fIapplied to some published data\fR (ELLEMTEL), Study Period\ 1981\(hy1984,
Geneva,\ 1984.
.LP
[12]
	CCITT Contribution COM XII\(hyNo. 4, \fIThe stability of the CCITT test\fR 
\fIteam\fR . Some comments. (ELLEMTEL), Study Period\ 1985\(hy1988,
Geneva,\ 1985.
.LP
[13]
	CCITT Contribution COM XII\(hyNo. 1, Question 15/XII (Annex 2),
\fIAdapting loudness ratings for transmission planning\fR , Study Period\ 
1985\(hy1988. 
.LP
[14]
	Private Communication from FTZ (Federal Republic of Germany).
.LP
[15]
	CCITT Contribution COM XII\(hyNo. 15, \fIObjective measurement and\fR 
\fIcalculation of the reference attenuation of local cables\fR (Sweden), Study
Period\ 1964\(hy1968.
.LP
[16]
	CCITT Contribution COM XII\(hyNo. 111, \fISubjective and objective\fR 
\fIcomparison of results concerning loudness ratings (LR) and R25\ equivalents\fR 
\fI(R25E)\fR , Study Period\ 1985\(hy1988. 
.LP
[17]
	 CCITT Contribution COM XII\(hyNo. 58, \fIDetermination of loudness ratings\fR 
\fIand R25\ equivalents for operator headsets, taking acoustical leakage 
into\fR 
\fIaccount\fR , Study Period\ 1985\(hy1988.
.LP
[18]
	 CCITT Contribution COM XII\(hyD.44 \(em WPXII/2 \(emShanga\*:i, 12\(hy16\ 
October\ 1987 Status Report of Question\ 17: \*QLoudspeaking telephones\*U 
(see COM XII\(hyR\ 20, 
Study Period\ 1985\(hy1988).
.LP
[19]
	CCITT Contribution COM XII\(hy235, \fISending objective measurements of\fR 
\fIhands\(hyfree sets. Influence of artificial voices characteristics\fR 
, Study 
Period\ 1985\(hy1988.
.LP
[20]
	ZWICKER, FELDTKELLER: Das Ohr als Nachrichtenempf\*:anger,
\fIS.\ Hirzel Verlag\fR , Stuttgart.
.LP
[21]
	PAULUS (E.) and ZWICKER (E.): Computer programmes for calculating
loudness from third\(hyoctave band levels or from critical band levels,
\fIAcustica\fR ,\ 1972, Vol.\ 27, pp.\ 253\(hy266.
.LP
[22]
	 CCITT Handbook on telephonometry (CERF: an equipment for the objective 
measurement of various sorts of loudness used by the French Postal and 
Telecommunication Administration), ITU, Geneva,\ 1987.
.LP
.rs
.sp 2P
.ad r
Blanc\fR 
.ad b
.RT
.LP
.bp