Low C, (C0,) is 16.35 Hz., and produced by the pipe organ, etc. Additionally, synthesized low frequency sound is used in DVD/movie production, (like Lucasfilms' "Return of the Jedi,") using Adobe Surround Sound, and Lucasfilms' THX specification, which specify as low as 5 Hz., (as specified in SMPTE RP 155.)

Although CDs are usually mastered with a 20 Hz. low frequency response, newer CDs do, indeed, contain frequencies that are lower-down to about 5 Hz.

The riff/wave files on various CDs were analyzed for low frequency content using the truly outstanding Baudline FFT time-frequency browser designed for scientific visualization of the spectral domain software, with the settings:

            Input->Devices->Sample Rate->44100
            Input->Devices->Decimate By->128

        

The noise floor of the computer sound card was measured at about -95 dB @ 5 Hz., and -105 dB at 50-130 Hz. (Notice the 1/f noise, which continues out to about 2 kHz.) The sound card used was a SoundBlaster/Ensoniq CT4810.

The following data was taken for specific tracks, (dB levels are relative):

            "Grazin' In The Grass," Bony James & Rick Braun, from
            the CD "Shake It Up," 2000, ISBN 9362-47557-2, which had
            an average level of approximately -45 dB from 50-140 Hz.,
            and an average level of -60 dB at 5 Hz., with peaks of -50
            dB at 5 Hz., (-60 dB at 14 Hz.)  -40 dB @ 30 Hz., dropping
            to -60 @ 20 Hz., flat to 5 Hz.

            "(Da La) Taleo," Carlos Santana, from the CD
            "Supernatural," 1999, ISBN 7822-19080-2, which had an
            average level of approximately -45 dB from 50-140 Hz., and
            an average level of -75 dB at 5 Hz., with peaks of -55 dB
            at 5 Hz, (-65 dB at 14 Hz.) -40 dB @ 50 Hz., dropping to
            -80 dB at 20 Hz., rising to -65 dB @ 5 Hz.

            "Smiles And Smiles To Go," Larry Carlton, from the CD
            "Larry Carlton Selection," 1990, ISBN 11105-9611-2, which
            had an average level of approximately -55 dB @ 30-150 Hz.,
            and an average level of -65 dB @ 5 Hz., with peaks of -45
            dB @ 5 Hz. (-80 dB at 14 Hz.)  -50 dB @ 35 Hz., dropping
            to -85 dB @ 20 Hz., rising to -65 dB @ 5 Hz.

        

The release dates cover about the last decade and a half.

Note that the ratio of the peak level to average program level at 5 Hz. differs by about 10-20 dB, (15 dB is the specification for CDs, 18 dB for DVDs,) which is reasonable-the ratio of peak to program level remains about the same at 5 Hz. and 100 Hz. The ratio of the program level at about 100 Hz. to the program level at 5 Hz. is about 10-15 dB, a factor of 10 to 32.

Note that producing 5 Hz. from a speaker system in a room requires acoustically treated walls, walls/ceilings/floors that are not parallel to each other, and a minimum room dimension of 565 / 5 = 113 feet, i.e., specifically designed theaters.

Another option is headphones, which do, indeed, produce frequencies well below 20 Hz., at modest prices, (which probably accounts for their popularity among musicians and sound/recording/mixing engineers.)

Yet another option is to configure the speakers in a near field arrangement, where the speakers are much closer to the listener, (usually less than one meter,) and run at much lower power levels, such that the sound energy reflected from the walls/ceiling/floor is a much lower intensity than the sound from the speakers, (and the standing waves and reflections have much less consequence.) This alternative is often used in recording studios by musicians and sound/recording/mixing engineers for monitoring recordings. (Most recording studios have control rooms that are far too small to produce 5 Hz. program frequencies, however.)

A license is hereby granted to reproduce this design for personal, non-commercial use.

THIS DESIGN IS PROVIDED "AS IS". THE AUTHOR PROVIDES NO WARRANTIES WHATSOEVER, EXPRESSED OR IMPLIED, INCLUDING WARRANTIES OF MERCHANTABILITY, TITLE, OR FITNESS FOR ANY PARTICULAR PURPOSE. THE AUTHOR DOES NOT WARRANT THAT USE OF THIS DESIGN DOES NOT INFRINGE THE INTELLECTUAL PROPERTY RIGHTS OF ANY THIRD PARTY IN ANY COUNTRY.

So there.

Copyright © 1992-2008, John Conover, All Rights Reserved.

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