Another Python Freebie... An Audio Sweep Generator.

Bazza — Sat Dec 17, 2011 11:42 am

Author: Bazza

Posted: Sat Dec 17, 2011 11:42 am

Hi all...

DM might be interested in this little devil...

A Linux Python 3.x.x code to sweep the audio spectrum from 4KHz down
to 100Hz and back again. (It is effectively a siren sound.)

Written so that anyone can understand how it works...

I will be releasing a Python 2.x.x version to code.activestate.com soon.

Watch out for wordwrapping etc...

Enjoy finding simple solutions to often VERY difficult problems... ;o)

Code:

# SweepGen3x.py
#
# A DEMO Audio Sweep Generator from 4KHz down to 100Hz and back up again
# using standard Text Mode Python. Another kids level piece of code for a very
# simple, FREE, Test Gear project... Hey, it is not perfect but a simple audio
# sweep generator for FREE, what more could you want!
# This working idea is copyright, (C)2010, B.Walker, G0LCU.
# Initially issued to LXF under the MIT licence.
# Written in such a way that anyone can understand how it works.
#
# Tested on PCLinuxOS 2009 and Debian 6.0.0 using Python 3.1.3 and 3.2.2.
# "/dev/dsp" IS required for this to work; therefore if you haven't got it then
# install "oss-compat" from you distro's repository. Ensure the sound system is
# not already in use.
# It is easily possible to lengthen the higher frequency playing times and VERY
# easily alter the output level and to speed up or slow down the sweep speed.
# I'll let the big guns do that for you...
# IMPORTANT NOTE:- Every EVEN number of bytes is a symmetrical "square" wave BUT
# every ODD number of bytes has preference for the "space" by one byte.
#
# To run this DEMO type at the Python prompt......
#
# >>> exec(open("/full/path/to/SweepGen3x.py").read())<RETURN/ENTER>
#
# ......and away you go.
#
# Note:- NO import[s] required at all, good eh! ;o)

def main():
# Set all "variables" as globals, my choice... ;o)
global mark
global space
global freq
global stringlength
global n
global sweep

# Allocate initial values.
mark=b"\xff"
space=b"\x00"
freq=mark+space
# 8KHz is the default sample speed of the sound system.
# Therefore this sets the lowest frequency, 8KHz/80=100Hz...
stringlength=80
n=0
sweep=0

# A simple screen clear and user screen for a default Python window...
for n in range(0,40,1):
   print("\r\n")
print("Sweep Generator DEMO from 4KHz down to 100HZ and back again...\n")
print("This just gives 5 SIREN like sweeps but it is enough for this DEMO...\n")
print("Copyright, (C)2010, B.Walker, G0LCU.\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n")

# Open the audio device, "/dev/dsp" for writing.
audio=open("/dev/dsp", "wb")

# Sweep for five times only for this DEMO...
while 1:
   freq=mark+space
   stringlength=80
   n=0

   while sweep<=4:
      # Sweep down from 4KHz to 100Hz.
      audio.write(freq)
      # Add a trailing 0x00 byte.
      freq=freq+space
      # Quit when length of "freq" byte-string is 80 bytes.
      if len(freq)>=stringlength: break
      audio.write(freq)
      # Add a leading 0xff byte.
      freq=mark+freq
      # Quit when length of "freq" byte-string is 80 bytes.
      if len(freq)>=stringlength: break
   while 1:
      # Sweep back up again from 100Hz to 4KHz.
      # Start with an empty byte-string.
      freq=b""
      # Now create a new byte square wave byte-string.
      for n in range(0,int((stringlength)/2),1):
         freq=freq+mark
      for n in range(0,int((stringlength)/2),1):
         freq=freq+space
      audio.write(freq)
      # Create a new byte-string reduced by one byte.
      # This removes one 0xff byte.
      stringlength=stringlength-1
      # Quit when length of "freq" byte-string is 2 bytes.
      if len(freq)<=2: break
      # Start with an empty byte-string.
      freq=b""
      # Now create a new byte-string reduced by one byte.
      for n in range(0,int((stringlength)/2),1):
         freq=freq+mark
      for n in range(0,int(((stringlength)/2)+1),1):
         freq=freq+space
      audio.write(freq)
      # This removes one 0x00 byte.
      stringlength=stringlength-1
      # Quit when length of "freq" byte-string is 2 bytes.
      if len(freq)<=2: break
   sweep=sweep+1
   # Ensure a complete exit from the loop.
   if sweep>=5: break
# On exit ensure the audio device is closed.
audio.close()
main()

# End of SweepGen3x.py DEMO...
# Enjoy finding simple solutions to often VERY difficult problems... ;o)

Enjoy banging the metal and getting something useful for your home
electronics workbench...

Bazza, G0LCU...

Linux Format forums

Another Python Freebie... An Audio Sweep Generator.