bark_hertz.3

speech signal process tools

.\" Copyright (c) 1998 Entropic, Inc. All rights reserved.
.\" @(#)bark_hertz.3	1.1 9/4/98 ESI/ERL/EG
.ds ]W (c) 1998 Entropic, Inc.
.TH BARK_HERTZ 3\-ESPSsp 9/4/98
.SH NAME
bark_to_hz \- Convert a Bark scale value to the equivalent frequency in Hertz.
.br
hz_to_bark \- Convert a frequency in Hertz to the equivalent Bark-scale value.
.SH SYNOPSIS
.ft B
double 
.br
bark_to_hz (barkValue)
.br
double	barkValue;
.sp
.br
.ft B
double 
.br
hz_to_bark (freqValue)
.br
double	freqValue;
.SH DESCRIPTION
.PP
These functions are reciprocal functions that warp a linear-scaled frequency
value in Hertz to the equivalent Bark-scale value and back.
.PP
The frequency
.I f
in hertz corresponding to a Bark-scale value
.I b
is given by:
.IP
.if n \{\
f = 600 sinh (b/6)
\}
.if t \{\
.IR f " = 600 sinh (" b "/6)"
\}
.PP
as shown in ref. [1].
The conversion from a frequency value to a Bark scale value is done in the
obvious manner by
using the inverse hyperbolic function.
.SH EXAMPLE
.nf

double bigNumber = MAXFLOAT, hertz, bark;

/* bark_to_hz can exceed MAXDOUBLE */
errno = 0;
hertz = bark_to_hz(bigNumber);
if (errno)
  perror("bark_to_hz error");

/* reasonable frequency values are fine */
hertz = 5000.0;
bark = hz_to_bark(hertz);
printf("bark equivalent of 5000 Hz is %f", bark);

/* This makes the variable hertz = 5000.0 */
hertz = bark_to_hz(bark);
printf("bark value converted by to hertz is %f", hertz);
.fi
.SH WARNINGS
In general, these functions should not be used with negative valued inputs.
No checking is done, however, by these functions.
.SH BUGS
None known.
.SH SEE ALSO
.nf
\fImel_to_hz\fP(3-ESPS), \fIhz_to_mel\fP(3-ESPS), \fIbarkspec\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 \fIbarkspec\fP(1\-ESPS) by David Burton; manual page by David Burton.