Intermodulation test signal

[BitPoint]

Hi,

Does anyone have the two-tone test signal (19 & 20 kHz, -3dBFS each tone) so that I can burn it into a CD. I want to use this signal to performance a intermodulation test for my PA.

Many thanks,

BitPoint

[dusfor99]

Originally posted by BitPoint
Hi,

Does anyone have the two-tone test signal (19 & 20 kHz, -3dBFS each tone) so that I can burn it into a CD. I want to use this signal to performance a intermodulation test for my PA.

Many thanks,

BitPoint

Hi BitPoint,

You will need -6dBFS each so it doesn't clip. If you can get a matlab script, here is the code to generate the test tone

clc;
TT = 60; %Total Time of Track in seconds
FS = 44.1e3; %Sample Rate
dB = 0; %Amplitude in dB
BITS = 16; %Number Of Bits Per Sample
F1 = 19e3; %Frequency 1
F2 = 20e3; %Frequency 2

AMP = 10^(dB/20) - .0001;
y =(AMP)*sin(2*pi*F1.*[0:1/FS:TT])/2 +(AMP)*sin(2*pi*F2.*[0:1/FS:TT])/2;
track = ['44p1k_19k_20k_16b.wav'];
wavwrite([y' y'],FS,BITS,track);



Dustin

[Javin5]

Hi BitPoint

Just in case you don't have matlab, I can send you a test signal as an email attachment. Send me your email address and tell me the maximum capacity you can handle. A one minute wav-file is approx. 10.6 MB.

Kurt

[Javin5]

A word of caution: Be absolutely sure that amp and speakers are disconnected when you test with the CD. A 20 kHz tone at full level could easily destroy your tweeters!

[phofman]

You can do miracles with open source SoX http://sox.sourceforge.net/ .

sox -V -r 44100 -c 2 -b 16 -t wav -n intermodul.wav synth 300 sine create 20000 synth sine mix 19000

Reads: create file intermodul wav with the same parameters as the non-existent input file (-n): fs 44100, 2 channels, 16 bits per sample, format wav. Apply the effect synth for 300 secs in mode create generating sine 20000Hz, chain another effect synth in mode mix generating sine 19000Hz. To prevent clipping, the mode mix halves the amplitude of input and generated signals automatically.

You can check spectrum of the resultant file by running

sox intermodul.wav -n remix 1 spectrogram -y 4

Cropped resultant picture spectrogram.png:

[PA0SU]

Every decent audio editer will generate the signals you want!