phon_to_sone.3

speech signal process tools

.\" Copyright (c) 1998 Entropic, Inc. All rights reserved.
.\" @(#)phon_to_sone.3	1.1 9/4/98 ESI/ERL/EG
.ds ]W (c) 1998 Entropic Research Laboratory, Inc.
.TH PHON_TO_SONE 3\-ESPSsp 9/4/98
.SH NAME
phon_to_sone \- Convert loudness level in phons to subjective loudness in sones
.SH SYNOPSIS
.ft B
double 
.br
phon_to_sone(phonValue)
.br
double	phonValue;
.SH DESCRIPTION
.PP
The increase in level (phons) needed to double the subjective
loudness is not constant with loudness level.
This function nonlinearly compresses the phon loudness scale 
in the audible region to 
better match the subjective loudness scale (sones). See [1] and its references
for details.
.PP
The level in 
.I sones
corresponding to a loudness level in
.I phons 
is given by:
.IP
\fIsoneValue = 2^(phonValue \- 40)/10\fP
.PP
The input phon level is in dBs.
.SH EXAMPLE
.nf

double sone, phon, bigNumber = 10000;

/* phon_to_sone may exceed MAXDOUBLE */
errno = 0;
sone = phon_to_sone(bigNumber);
if (errno)
  perror("phon_to_sone error");

/* reasonable frequency values are fine */
phon = 100;
sone = phon_to_sone(phon);
printf("sone equivalent of 100 phons is %f", sone);
.fi
.SH WARNINGS
In general, this function should not be with a negative valued input.
No checking is done, however, by this function.
.SH BUGS
None known.
.SH SEE ALSO
.nf
\fIbs_dist\fP(1\-ESPS)
.fi
.SH REFERENCES
.HP
[1] S. Wang, A. Sekey, and A. Gersho,
``An objective measure for predicting subjective quality of speech coders,''
.I "IEEE Journal on Selected Areas in Communications,"
.BR SAC-10
(5), 819\-829 (June 1992)
.sp
.SH AUTHOR
Code extracted from \fIbs_dist\fP(1\-ESPS) by David Burton; manual page by David Burton.