notchfilt.1

来自「speech signal process tools」· 1 代码 · 共 206 行

.\" Copyright (c) 1987 Entropic Speech, Inc.; All rights reserved
.\" @(#)notchfilt.1	3.9	9/1/98 ESI
.TH NOTCH_FILT 1\-ESPS 9/1/98
.ds ]W "\fI\s+4\ze\h'0.05'e\s-4\v'-0.4m'\fP\(*p\v'0.4m'\ Entropic Speech, Inc.
.SH NAME
notch_filt \- design a second order notch filter.
.SH SYNOPSIS
.B notch_filt
[
.BI \-P " param_file"
]
[
.BI \-x " debug_level"
]
[
.BI \-s " samp_freq"
]
[
.BI \-n " notch_freq"
]
[
.BI \-b " band_width"
]
[
.BI \-g " gain"
]
.I feafilt_file
.SH DESCRIPTION
.PP
The program
.I notch_filt
designs an IIR notch filter and writes the coefficients to the
.IR FEA_FILT (5\-ESPS)
file
.I feafilt_file.
The user must specify the sampling frequency, the frequency of the notch center,
and the desired notch bandwidth.  These parameters may be specified in the parameter
file, or on the command line.
The notch bandwidth 
is defined as the distance in the frequency domain between
the \-6 dB. points (magnitude) on either side of the notch.
.PP
If
.I feafilt_file
is "\-", the output goes to the standard output.
.PP
Use \fIfiltspec(1-ESPS)\fR to compute the actual filter response; use
\fIplotspec(1-ESPS)\fR to view the response.  For example, 
.PP
\fIfiltspec feafilt_file - | plotspec -\fR
.SH OPTIONS
The following options are supported:
.TP
.BI \-P " param_file"
The file 
.I param_file
is used for the parameter file instead of the default, which is
.I params.
.br
.TP
.BI \-x " debug_level"
A value of 0 (the default value) will cause
.I notch_filt
to do its work silently, unless there is an error.
A nonzero value will cause various parameters to be printed out
during program initialization.
.br
.TP
.BI \-s " samp_freq"
The value
.I samp_freq
is used for the sampling frequency instead of the value given in the 
parameter file.
.br
.TP
.BI \-n " notch_freq"
The value
.I notch_freq
is used for the notch frequency instead of the value given in the 
parameter file.
.br
.TP
.BI \-b " band_width"
The value
.I band_width
is used for the notch bandwidth instead of the value given in the 
parameter file.
The notch bandwidth is defined as the distance (in Hz.) between the \-6 
dB points
on either side of the notch frequency in the magnitude response spectra.
.br
.TP
.BI \-g " gain"
The d.c. gain of the filter.  The default is 1.0.
.br
.SH ESPS PARAMETERS
.PP
The values of parameters obtained from the parameter file are printed
if the environment variable ESPS_VERBOSE is 3 or greater.  The default
value is 3.
.PP
The following parameters are read from the parameter file if they are not
entered on the command line.  If all three values are provided on the command
line then the parameter file need not be provided.
.sp .5
.TP
.I "samp_freq \- float"
The value of the sampling frequency.
.TP
.I "notch_freq \- float"
The value of the notch frequency.
.TP
.I "band_width \- float"
The value of the notch bandwidth.
The notch bandwidth is defined as the distance (in Hz.) between the -6 dB points
on either side of the notch frequency in the magnitude response spectra.
.sp .5
.SH ESPS COMMON
Esps Common is not processed.
.sp .5
.SH ESPS HEADER
A new
.IR FEA_FILT (5\-ESPS)
header is created for the output file.
The program fills in 
values in the common part of the header
as well as the generic header items associated with the
.IR FEA_FILT (5\-ESPS)
file type.
.sp .5
.TP
.I max_num
This value is always set to 3.
.TP
.I max_denom
This value is always set to 3.
.TP
.I complex_filter
These values are always set to NO.
.TP
.I define_pz
This value is set to YES.
.TP
.I func_spec
This value is set to BAND.
.TP
.I nbands
This value is set to 3.
.TP
.I type
This value is set to BS.
.TP
.I method
This value is set to PZ_PLACE.
.TP
.I band edges
There are six values entered in this array corresponding to the three frequency
"bands".  The band edges of band #1 will be 0 Hz. and the lower \-6 
dB. point.
The band edges of band #2 are both set 
to the notch frequency.  The band edges
of band #3 will be the upper \-6 dB. point and half the sampling frequency.
.TP
.I gains
There are three values in this 
array corresponding to the three frequency "bands".
The values are set to 
.I gain,
0.0, and
.I gain.
.LP
In addition, three generic header items are added: \fIsamp_freq,
notch_freq,\fR and \fIband_width\fR.
.TP
.I "samp_freq \- double"
The sampling frequency is stored here.
.TP
.I "notch_freq \- double"
The center frequency of the notch is stored here.
.TP
.I "band_width \- double"
The 6 dB bandwidth of the notch is stored here. 
.LP
The fields \fInum_degree\fP and \fIdenom_degree\fP in the output
records are always set to 3.  The filter pole and zero locations 
are written to the output file.
.sp .5
.SH DIAGNOSTICS
The program prints a message to the standard error output and exits if 
.I nf
is not less than one half the sampling frequency or if
.I nf
+/\-
.I bw/2
does not fall in the range from zero Hz. to one half the sampling frequency.
.SH SEE ALSO
.IR FEA (5\-ESPS), 
.IR FEA_FILT (5\-ESPS),
.IR filter (1\-ESPS), 
.br
.IR wmse_filt (1\-ESPS),
.IR xpz (1\-ESPS),
.IR iir_filt (1\-ESPS)
.SH AUTHOR
Brian Sublett.  FEA_FILT modifications by Bill Byrne.