Dear Editor (Sept. 1979)

Aural Fatigue on Planes

Dear Sir:

In the May issue of Audio, correspondent Joel Tall wonders, "Why is it that airplane designers are not aware that the noise inside the 'usual' plane destroys hearing?" Lest readers of Audio become alarmed by this reference to hearing damage from riding in airplanes, I'd like to report the results of my findings of several years ago, when I, too, became concerned about possible hearing damage from extended exposure to airline travel.

For about three months, I took a Scott 450 instrumentation-grade sound level meter with me on all flights, covering in the process a variety of seating positions in all the models of commercial jets then flying. As you would expect, the highest noise readings I got were in window seats toward the rear of the aircraft and during METO conditions (take-off and shortly after).

While I observed many broad-band (C-weighted) readings in the mid-eighties, the highest A-weighted reading I got in any commercial airliner was 79 dB SPL, well below the level at which hearing damage can occur.

Aural fatigue as mentioned by writer Tall is quite another matter from hearing damage, and in this I agree with Tall. I certainly would not like to do a recording session within a day after a transatlantic flight, or even a domestic flight for that matter. But it should be noted that jetliner fatigue, while an inconvenience, is not a hearing health hazard, and it should not be characterized as damaging to the aural facility.

Bruce Mallon; Stoneham, Mass.

More on Ear Fatigue

Dear Editor:

Following up the letter in the May issue of Audio on air travel and its effects on hearing, I was once a student of aviation. Back when I took flight instruction, I was informed that the low frequency waves, a.k.a. "the vibratory jet noise penetrating the cabin" can and does cause deafness in pilots.

To pilots, it is something to be reckoned with.

-Don Rima, II; Tamassee, S.C.

Audio Evolution

Dear Sir:

William A. Manly's article "Phase, Time, Ears, and Tape" in the April, 1979, issue of Audio was both important and timely.

Frequency response, as we now think of it and as we now graph it, was not "discovered" until the 1920s (see Bostwick," Acoustic Considerations Involved in Steady-State Loud Speaker Measurements," Bell System Technical Journal 8:1, p. 135, Jan., 1929). Fifty years later all the wrinkles are still not fully understood (see Bordone-Sacer dote, "Round Robin Measurements on Loudspeaker Systems" Acustica, 38:5, pp. 297-312, Nov., 1971).

In the same way, phase response has been "discovered" in the 1970s. We have come to realize that phase response must be under control (if not ruler flat) at every step ... in the microphone, throughout the recording channel (as Mr. Manly describes), through all the processing equipment, and out through the loudspeaker. We will fully understand phase response at about the same time we fully under stand frequency response ... maybe some time in the next century, maybe never.

-Ted Uzzle; Cambridge, Mass.

Birth of a New Spec?

Dear Editor:

Mr. Wilson's comments regarding his rear-end crash published in the April issue could well lead to a new FCC spec, "Crash Absorption, Foot-Pounds Per Channel." Just what we need--more government regulations, perhaps with a minimum "capable of withstanding a 55 m.p.h. rear-end crash with no more than 0.2 percent damage." Possibly Professor I. Lirpa can integrate this sturdy specification in his new four-wheel drive VDRS.

-Edward T. Dwyer; Manahawkin, N.J.

Shower Singer Seeks Advice

Dear Sir:

Playing a live "shower record" made while using the Lirpa Shower Mike (reviewed in the April issue), I heard a horrible "iss" sound.

Is this sound due to:

a) Deficient circuitry in the mike, or

b) The noise of the water coming from the shower? If the latter is the cause, is Professor I. Lirpa currently working on a noise reduction invention for home showers? Your reply is very important to me, a shower singer lover.

-J. C. Picarra Sao Paulo, Brazil

Since there is no circuitry in the microphone, we can rule out the hypothesis proffered in "a." Therefore, assuming "b" is correct, we can get round the horrible "iss" by eliminating the water from the shower head which will contribute mightily to the mike's reliability, as per Figs. 5 and 6 in the original review.

-E.P.

Classical Tapes Offered

Dear Sir:

My late husband had, in the last 13 years, amassed a collection of classical tapes which I am interested in selling in its entirety.

The collection is completely catalogued. It is on reel-to-reel tape, re corded from Chicago's WFMT classical music station, on an Ampex tape deck.

The collection includes Bach; Beethoven; Berlioz; Britten; Bruckner; Delius; Donizetti; English orchestral and folk songs; Franck; French art songs; German lieder; Haydn; Ives; Janacek; Mahler; Mozart; Poulenc; Purcell; various Russian, Spanish, Scandinavian, and Polish music; Schubert;

Schumann; Schoenberg; Shostakovich; Stravinsky, and others. There are approximately 1,300 tapes of excellent quality in the collection.

Interested individuals may write to me at the below address.

Kathleen M. Disselhorst, 10525 South Hale Chicago, III. 60643

Audio Pen Pal Sought

Dear Sir:

I am a 20-year-old Czech student, with a passionate interest in music and hi-fi. I would like to correspond with readers of similar interests and possibly exchange records.

Vaclav Jerabek Kodanska 29 101 00 Praha 10 Czechoslovakia

(Source: Audio magazine, Sept. 1979)

Also see: Dear Editor (Mar. 1980)

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