The first track is an octave band of pink noise centered at 1 kHz, uncorrelated in the two channels. Its average level is -15 dBFS. The "standard" level for our tests was a system gain that provided realistic, loud, clear sound from most of the tracks we used. We had to add about 10 dB to this gain to reliably hear the noise floor of the 16-bit processor with no music playing. At our standard gain, the test signal produced a C-weighted sound level of 85 dB at the primary listening chair.

This MP3 file is the level setting signal mentioned in the paper on the audibility of a CD-quality loop inserted into a high-bit audio stream, by E. Brad Meyer and David Moran, published in the September, 2007 issue of the Journal of the Audio Engineering Society. The reference system gain mentioned in the paper can be duplicated by playing this signal, a one-octave band of pink noise centered on 1 kHz, so that the level at your listening chair is 85 dB SPL

File 2 is the same as track #20 from our BAS Test CD. If you read this paragraph from the BAS Test CD Liner Notes, you will understand the philosophy:

Track 21 is borrowed with permission from Tomlinson Holman's Hollywood Edge test CDs, where it is billed as a high-frequency limit test for your system. It is of course no such thing, as Holman admits with little prodding; modern tweeters all go out to 20 kHz or beyond, but aging listeners do not. Holman's test is a tone that starts at 8 kHz and sweeps upward. You track the sound, starting at 8 kHz and reading the index points that occur every 0.5 kHz, noting when the tone seems to disappear.

The test works, but it requires the listener to say when he or she stops hearing sound — which is more difficult than the opposite, so we reversed the signal and put our version first, on track 20. Our tone begins at 20 kHz, and you can find out how badly you've treated your hearing over the years by reading the numberof seconds from the beginning of the track at which the tone becomes audible and consulting the table below.

(Four test CDs, titled Electroacoustical Tests, Acoustic Tests, Digital and Analog Tests and Stereo & Surround System Setup and Test are available from The Hollywood Edge, (213) 466-6723 or www.hollywoodedge.com.)

High-frequency limit, downward sweep
Note: If your player displays index marks subtract one from the mark at which the tone becomes audible and read the frequency from the table.