ref: f7e3b7d8c96e749df08bbb06ce887770df100ce8
dir: /soxexam.7/
'\" t
'\" The line above instructs most `man' programs to invoke tbl
'\"
'\" Separate paragraphs; not the same as PP which resets indent level.
.de SP
.if t .sp .5
.if n .sp
..
'\"
'\" Replacement em-dash for nroff (default is too short).
.ie n .ds m " -
.el .ds m \(em
'\"
'\" Placeholder macro for if longer nroff arrow is needed.
.ds RA \(->
'\"
'\" Decimal point set slightly raised
.ds d \v'-.15m'.\v'+.15m'
'\"
.TH SoX 7 "January 31, 2007" "soxexam" "Sound eXchange"
.SH NAME
soxexam\*mSoX Examples
.SH SYNOPSIS
.nf
\fBsox\fR [\fIglobal-options\fR] [\fIformat-options\fR] \fIinfile1\fR
[ [\fIformat-options\fR] \fIinfile2\fR ] ... [\fIformat-options\fR] \fIoutfile\fR
[\fIeffect\fR [\fIeffect-options\fR] ] ...
.SP
\fBplay\fR [\fIgeneral-options\fR] [\fIformat-options\fR] \fIinfile1\fR
[ [\fIformat-options\fR] \fIinfile2\fR ] ... [\fIformat-options\fR]
[\fIeffect\fR [\fIeffect-options\fR] ] ...
.SP
\fBrec\fR [\fIgeneral-options\fR] [\fIformat-options\fR] \fIoutfile\fR
[\fIeffect\fR [\fIeffect-options\fR] ] ...
.fi
.SH DESCRIPTION
.SS Introduction
The core problem is that you need some experience in using effects
in order to say `that any old sound file sounds with effects
absolutely hip'. There isn't any rule-based system which tell you
the correct setting of all the parameters for every effect.
But after some time you will become an expert in using effects.
.SP
Here are some examples which can be used with any music sample.
(For a sample where only a single instrument is playing, extreme
parameter setting may make well-known `typically' or `classical'
sounds. Likewise, for drums, vocals or guitars.)
.SP
Single effects will be explained and some given parameter settings
that can be used to understand the theory by listening to the sound file
with the added effect.
.SP
Using multiple effects in parallel or in series can result either
in a very nice sound or (mostly) in a dramatic overloading in
variations of sounds such that your ear may follow the sound but
you will feel unsatisfied. Hence, for the first time using effects
try to compose them as minimally as possible. We don't regard the
composition of effects in the examples because too many combinations
are possible and you really need a very fast machine and a lot of
memory to play them in real-time.
.SP
However, real-time playing of sounds will greatly speed up learning
and/or tuning the parameter settings for your sounds in order to
get that `perfect' effect.
.SP
Basically, we will use the `play' front-end of SoX since it is easier
to listen sounds coming out of the speaker or earphone instead
of looking at cryptic data in sound files.
.SP
For easy listening of file.xxx (`xxx' is any sound format):
.SP
play file.xxx effect-name effect-parameters
.SP
Or more SoX-like (for `dsp' output on a UNIX/Linux computer):
.SP
sox file.xxx \-t ossdsp \-w \-s /dev/dsp effect-name effect-parameters
.SP
or (for `au' output):
.SP
sox file.xxx \-t sunau \-w \-s /dev/audio effect-name effect-parameters
.SP
And for date freaks:
.SP
sox file.xxx file.yyy effect-name effect-parameters
.SP
Additional options can be used. However, in this case, for real-time
playing you'll need a very fast machine.
.SP
Notes:
.SP
I played all examples in real-time on a Pentium 100 with 32 MB and
Linux 2.0.30 using a self-recorded sample ( 3:15 min long in `wav'
format with 44\*d1 kHz sample rate and stereo 16 bit ).
The sample should not contain any of the effects. However,
if you take any recording of a sound track from radio or tape or CD,
and it sounds like a live concert or ten people are playing the same
rhythm with their drums or funky-grooves, then take any other sample.
(Typically, less then four different instruments and no synthesizer
in the sample is suitable. Likewise, the combination vocal, drums, bass
and guitar.)
.SS Echo
.SP
An echo effect can be naturally found in the mountains, standing somewhere
on a mountain and shouting a single word will result in one or more repetitions
of the word (if not, turn a bit around and try again, or climb to the next
mountain).
.SP
However, the time difference between shouting and repeating is the delay
(time), its loudness is the decay. Multiple echos can have different delays and
decays.
.SP
It is very popular to use echos to play an instrument with itself together,
like some guitar players (Brain May from Queen) or vocalists are doing.
For music samples of more than one instrument, echo can be used to add a
second sample shortly after the original one.
.SP
This will sound as if you are doubling the number of instruments playing
in the same sample:
.SP
play file.xxx echo 0\*d8 0\*d88 60 0\*d4
.SP
If the delay is very short, then it sound like a (metallic) robot playing
music:
.SP
play file.xxx echo 0\*d8 0\*d88 6 0\*d4
.SP
Longer delay will sound like an open air concert in the mountains:
.SP
play file.xxx echo 0\*d8 0\*d9 1000 0\*d3
.SP
One mountain more, and:
.SP
play file.xxx echo 0\*d8 0\*d9 1000 0\*d3 1800 0\*d25
.SS Echos
Like the echo effect, echos stand for `ECHO in Sequel', that is the first echos
takes the input, the second the input and the first echos, the third the input
and the first and the second echos, ... and so on.
Care should be taken using many echos (see introduction); a single echos
has the same effect as a single echo.
.SP
The sample will be bounced twice in symmetric echos:
.SP
play file.xxx echos 0\*d8 0\*d7 700 0\*d25 700 0\*d3
.SP
The sample will be bounced twice in asymmetric echos:
.SP
play file.xxx echos 0\*d8 0\*d7 700 0\*d25 900 0\*d3
.SP
The sample will sound as if played in a garage:
.SP
play file.xxx echos 0\*d8 0\*d7 40 0\*d25 63 0\*d3
.SS Chorus
The chorus effect has its name because it will often be used to make a single
vocal sound like a chorus. But it can be applied to other instrument samples
too.
.SP
It works like the echo effect with a short delay, but the delay isn't constant.
The delay is varied using a sinusoidal or triangular modulation. The modulation
depth defines the range the modulated delay is played before or after the
delay. Hence the delayed sound will sound slower or faster, that is the delayed
sound tuned around the original one, like in a chorus where some vocals are
a bit out of tune.
.SP
The typical delay is around 40ms to 60ms, the speed of the modulation is best
near 0\*d25Hz and the modulation depth around 2ms.
.SP
A single delay will make the sample more overloaded:
.SP
play file.xxx chorus 0\*d7 0\*d9 55 0\*d4 0\*d25 2 \-t
.SP
Two delays of the original samples sound like this:
.SP
play file.xxx chorus 0\*d6 0\*d9 50 0\*d4 0\*d25 2 \-t 60 0\*d32 0\*d4 1\*d3 \-s
.SP
A big chorus of the sample is (three additional samples):
.SP
play file.xxx chorus 0\*d5 0\*d9 50 0\*d4 0\*d25 2 \-t 60 0\*d32 0\*d4 2\*d3 \-t 40 0\*d3 0\*d3 1\*d3 \-s
.SS Flanger
The flanger effect is like the chorus effect, but the delay varies between
0ms and maximal 5ms. It sound like wind blowing, sometimes faster or slower
including changes of the speed.
.SP
The flanger effect is widely used in funk and soul music, where the guitar
sound varies frequently slow or a bit faster.
.SP
Now, let's groove the sample:
.SP
play file.xxx flanger
.SP
listen carefully between the difference of sinusoidal and triangular modulation:
.SP
play file.xxx flanger triangle
.SS Reverb
The reverb effect is often used in audience hall which are to small or contain
too many many visitors which disturb (dampen) the reflection of sound at
the walls. Reverb will make the sound be perceived as if it were in
a large hall. You can try the reverb effect in your bathroom or garage or
sport halls by shouting loud some words. You'll hear the words reflected from
the walls.
.SP
The biggest problem in using the reverb effect is the correct setting of the
(wall) delays such that the sound is realistic and doesn't sound like music
playing in a tin can or has overloaded feedback which destroys any illusion
of playing in a big hall.
To help you obtain realistic reverb effects, you should decide first how
long the reverb should take place until it is not loud enough to be registered
by your ears. This is be done by varying the reverb time `t'. To simulate
small halls, use 200ms. To simulate large halls, use 1000ms. Clearly,
the walls of such a hall aren't far
away, so you should define its setting be given every wall its delay time.
However, if the wall is to far away for the reverb time, you won't hear the
reverb, so the nearest wall will be best at `t/4' delay and the farthest
at `t/2'. You can try other distances as well, but it won't sound very realistic.
The walls shouldn't stand to close to each other and not in a multiple integer
distance to each other ( so avoid wall like: 200 and 202, or something
like 100 and 200 ).
.SP
Since audience halls do have a lot of walls, we will start designing one
beginning with one wall:
.SP
play file.xxx reverb 1 600 180
.SP
One wall more:
.SP
play file.xxx reverb 1 600 180 200
.SP
Next two walls:
.SP
play file.xxx reverb 1 600 180 200 220 240
.SP
Now, why not a futuristic hall with six walls:
.SP
play file.xxx reverb 1 600 180 200 220 240 280 300
.SP
If you run out of machine power or memory, then stop as many applications
as possible (every interrupt will consume a lot of CPU time which for
bigger halls is absolutely necessary).
.SS Phaser
The phaser effect is like the flanger effect, but it uses a reverb instead of
an echo and does phase shifting. You'll hear the difference in the examples
comparing both effects.
The delay modulation can be sinusoidal or triangular, preferable is the
later for multiple instruments. For single instrument sounds,
the sinusoidal phaser effect will give a sharper phasing effect.
The decay shouldn't be to close to 1 which will cause dramatic feedback.
A good range is about 0\*d5 to 0\*d1 for the decay.
.SP
We will take a parameter setting as before (gain-out is
lower since feedback can raise the output dramatically):
.SP
play file.xxx phaser 0\*d8 0\*d74 3 0\*d4 0\*d5 \-t
.SP
The drunken loudspeaker system (now less alcohol):
.SP
play file.xxx phaser 0\*d9 0\*d85 4 0\*d23 1\*d3 \-s
.SP
A popular sound of the sample is as follows:
.SP
play file.xxx phaser 0\*d89 0\*d85 1 0\*d24 2 \-t
.SP
The sample sounds if ten springs are in your ears:
.SP
play file.xxx phaser 0\*d6 0\*d66 3 0\*d6 2 \-t
.SS Compander
The compander effect allows the dynamic range of a signal to be
compressed or expanded.
For most situations, the attack time (response to the music getting
louder) should be shorter than the decay time because our ears are more
sensitive to suddenly loud music than to suddenly soft music.
.SP
For example, suppose you are listening to Strauss' `Also Sprach
Zarathustra' in a noisy environment such as a car.
If you turn up the volume enough to hear the soft passages over the
road noise, the loud sections will be too loud.
You could try this:
.SP
play file.xxx compand 0\*d3,1 \-90,\-90,\-70,\-70,\-60,\-20,0,0 \-5 0 0\*d2
.SP
The transfer function (`\-90,...') says that
.I very
soft sounds between \-90 and \-70 decibels (\-90 is about the limit of
16-bit encoding) will remain unchanged.
That keeps the compander from boosting the volume on `silent' passages
such as between movements.
However, sounds in the range \-60 decibels to 0 decibels (maximum
volume) will be boosted so that the 60dB dynamic range of the
original music will be compressed 3-to-1 into a 20dB range, which is
wide enough to enjoy the music but narrow enough to get around the
road noise.
The \-5 dB output gain is needed to avoid clipping (the number is
inexact, and was derived by experimentation).
The 0 for the initial volume will work fine for a clip that starts
with a bit of silence, and the delay of 0\*d2 has the effect of causing
the compander to react a bit more quickly to sudden volume changes.
.SS Changing the Rate of Playback
You can use stretch to change the rate of playback of an audio sample
while preserving the pitch. For example to play at half the speed:
.SP
play file.wav stretch 2
.SP
To play a file at twice the speed:
.SP
play file.wav stretch 0\*d5
.SP
Other related options are `speed' to change the speed of play
(and changing the pitch accordingly), and pitch, to alter the
pitch of a sample. For example to speed a sample so it plays in
half the time (for those Mickey Mouse voices):
.SP
play file.wav speed 2
.SP
To raise the pitch of a sample 1 while note (100 cents):
.SP
play file.wav pitch 100
.SP
.SS Reducing noise in a recording
.SP
First find a period of silence in your recording, such as the beginning or
end of a piece. If the first 1\*d5 seconds of the recording are silent, do
.SP
sox file.wav \-n trim 0 1\*d5 noiseprof /tmp/profile
.SP
Next, use the noisered effect to actually reduce the noise:
.SP
play file.wav noisered /tmp/profile
.SH SEE ALSO
.BR sox (1),
.BR libst (3)
.SH AUTHOR
This manual was written by Juergen Mueller (jmueller@uia.ua.ac.be).
Other SoX authors and contributors are listed in the AUTHORS file that
is distributed with the source code.