These files may be of use for audio testing purposes. Except as noted,
they are in standard Windows "wav" format, in .zip packages. Short descriptive text items
are included within the wav files, in case you have a wav player/editor
capable of reading them (such as CoolEdit).
All samples are ten seconds long, except as noted. Most can be concatenated if needed, since all are set to begin and end on zero-cross.
Where applicable, the zip files also contain a .png image of the spectrograph or spectrogram of the corresponding wav file. A text version of this descriptive page is also available as 0_readme.txt.
|white.zip||this is "white noise," with a frequency distribution of 1 (i.e. all components of equal intensity). As seen from the spectrograph, this corresponds to a "flat" response.|
|pink.zip||this is "1/f noise," with a frequency distribution of 1/f, or a 3 dB per octave roll-off. It is generally considered the kind of noise most prevalent in nature.|
|brown.zip||this variety derives its name from "Brownian motion", and is the kind of noise associated with such "random walks." It has a frequency distribution of 1/(f^2), which is to say a roll-off of 6 dB per octave.|
|blue.zip||this is, in a sense, the inverse of "pink" noise, with a frequency increase of 3 dB per octave. Intensity is proportional to f.|
|violet.zip||and this is the inverse of "brown" noise, with a frequency premphasis of 6 dB per octave, or an intensity characteristic of f^2.|
|sweeplin.zip||this starts with one second of 20 Hz, followed by a fast "sync pulse" which might conceivably be useful for synchronizing a storage 'scope. Immediately thereafter, it sweeps linearly from 20 Hz. to 20 kHz. at a level of -3 dB (relative to 0 dB = 100% modulation). Total duration of the sweep is ten seconds.|
|3stepoct.zip||this file would be more useful for "manual" frequency response measurement. Unlike the other files, this is in mp3 format; I suggest converting it to a wav file first, an easy way to do this is to use WinAmp's "DiskWriter" output plug-in (ships with current versions). It has two-second samples of fixed tones from 20 Hz. to 20480 Hz, spaced logarithmically in 1/3 octave increments, for a total of 31 samples. The actual frequencies are included in the ID3 tag in the mp3 file itself, and are also shown in the .png spectrogram.|
|square.zip||this contains square waves at four different frequencies: 10 Hz, 100 Hz, 1 kHz, and 7.35 kHz. (The 7.35 kHz rate was chosen to avoid artifacts due to digital aliasing.)|
|bursts.zip||this file contains three separate files containing tone bursts. These
would be useful for checking amplifier transient response. All have a
repetition rate of 10 bursts per second, so it would be useful to set
your oscilloscope for a horizontal scan rate of 5 Hz.
|imd_smpte.zip||this contains 10 seconds of 60 Hz. at -3 dB, superimposed on 7000 Hz. at -12 dB, in compliance with the SMPTE/DIN standard for intermodulation distortion measurement for audio equipment. If you don't have a way of getting a spectrograph of your amplifier's response, this still might be useful in an auditory test; both tones should be pure and clean, with no warbling or "edginess" to them, and no additional audible artifacts. Try it at different volume levels, you'll readily hear if your system has excessive IMD especially at high volume; the low note will become progressively brassier, and the high tone will begin to warble as IMD increases.|
|imd_7350.zip||essentially the same idea, except that the high tone is 7350 Hz. (an even sub-multiple of the 44,100 Hz. sample rate) to prevent the possibility of aliasing artifacts affecting your measurements.|