April 11, 2005

Q: Why do some CDs, even ones labeled "DDD," seem to produce rumble?

Joe

A: They don’t produce rumble, but they’re pretty adept at reproducing it. Many recordings, particularly classical ones, are made in less-than-ideal locations, at least as far as extraneous noise is concerned, and this can affect the final product, whether digital or analog.

Classical music is commonly recorded in actual concert halls because of their acoustics, but such venues are rarely isolated from outside sounds in the way a recording studio is. Obvious intrusions -- jets flying over, police sirens -- can be prevented either by re-recording the interrupted passages and editing out the noise, or by choosing another location.

Low-frequency sounds -- the "rumble" you are hearing -- are more difficult to eliminate. Most are caused by traffic near the recording site, or mechanical noise (such as air-conditioning) within it. These sometimes crop up on recordings because the engineers can’t hear them -- monitor speakers, particularly those used on location, rarely produce as good bass as a first-class home system.

There’s nothing new about this -- subwoofer owners have been discovering such sounds on analog recordings for years. But with theoretically "perfect" digital media, perhaps we’re less inclined to forgive audible flaws.

…Ian G. Masters