Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!husc6!mit-eddie!ll-xn!ames!lll-tis!ptsfa!ihnp4!inuxc!iuvax!silver!commgrp From: commgrp@silver.bacs.indiana.edu Newsgroups: sci.electronics Subject: Re: Injury via Phone Message-ID: <24300015@silver> Date: Mon, 24-Aug-87 12:25:00 EDT Article-I.D.: silver.24300015 Posted: Mon Aug 24 12:25:00 1987 Date-Received: Tue, 25-Aug-87 06:38:12 EDT References: <414@gtx.com> Organization: Indiana University BACS, Bloomington Lines: 73 Nf-ID: #R:gtx.com:-41400:silver:24300015:000:3480 Nf-From: silver.bacs.indiana.edu!commgrp Aug 24 11:25:00 1987 In article <414@gtx.com>, al@gtx.com (0732) writes: > One often hears about people blowing whistles or air horns into a > telephone to thwart obscene callers. Is a telephone capable of > transmitting enough sound amplitude to cause pain or damage to the ears? > If so, this seems to be a dangerous capability in the hands of some crank. Larry Lippmann responds: > ...it is improbable that sufficient acoustic energy (sound >pressure level in dB) could be created such that physiological injury >would occur. > > ...As a combination EE/biochemist with a multidisciplinary >background, I have done some forensic science consulting for a number >of years. About ten years ago, I was retained as a consultant in a >workmen's compensation case. It seems that a middle-aged woman who >had worked as a switchboard operator for 20-some years had applied for >compensation resulting from partial hearing loss in one ear. Her >allegation was that then presence of clicks and loud noises in her >"headset ear" over many years caused her hearing loss. My function >was to work with an otolaryngologist to disprove her claim. > > My first reaction was that there was insufficient sound pressure >level to cause such injury. However, I learned that for the past five >years the woman used a Plantronics miniature headset (the kind with a >flexible plastic ear tube). Now with such a headset, there was an >almost perfect sound conduction between the receiver element and the >ear. So, we contacted Plantronics and got some engineering >information. We got a sample headset and conducted our own sound >pressure measurements using a Bruel & Kjaer "artificial ear". The >conclusion was that the maximum sound pressure level which could be >experienced through this headset in a switchboard environment was >still insufficent (by generally accepted medical criteria) to cause >hearing impairment. > > But the use of a receiver with a plastic ear tube did make me >seriously consider the possibility of injury. The big danger of plastic ear tubes, as in Plantronics headsets, is transmission of ear infection if headsets are shared. Wearing such a device, even if clean, for long periods might help incubate ear infections. Plantronics' latest models use a lightweight conventional external earphone instead of the ear tube. I like Plantronics headsets, especially the old model MS-50 with the headband (as worn upside-down by Clint Eastwood in the airplane hijacking scene in "Dirty Harry"). Plantronics headsets configured for telephone service are available for $10 to $20 at hamfests (regional gatherings of ham radio operators). They are easily modified for radio service; I use them while flying, and with my mobile and handheld ham rigs. I also have a custom-made hard plastic earmold with an external bar for mounting the MS-50, and a flexible tube to connect to the earphone output. It's very comfortable, and ideal for emergency service and high-noise environments. (Kits are available for making your own ear impression, which is mailed back to the company which makes the finished product.) reference: ---------- Reid, F. "Using Simulated Carbon Microphones with Amateur Trans- mitters" _Ham Radio_ magazine, Oct. 1981 p. 18. -- Frank Reid PO Box 5283 Bloomington, IN 47402 reid@gold.bacs.indiana.edu