LETTER TO THE EDITOR: Long-range acoustic devices have purpose, place, policy

Wednesday, October 12, 2011 | 5:56 p.m. CDT

Thank you for the opportunity to write to your publication regarding the article, "MU professor first to sue over long-range acoustic devices article" (Oct. 10).

This lawsuit was first reported Sept. 21 by Joe Mandak for The Associated Press and Rich Lord for the Pittsburgh Post-Gazette.

Both reports included quotes attributed to Karen Piper where she states she was “100 feet away” when Pittsburgh Police Department activated one of its long-range acoustic devices.

LRAD broadcasts follow the inverse square law, which teaches that for every doubling of the distance from the sound source, sound intensity diminishes by 6 decibels.

Like all loudspeakers, LRAD’s audio output is measured in decibels at a distance of 1 meter in front of the device.

Assuming that the largest LRAD system used at the Pittsburgh G20 Summit was activated at maximum volume, the sound pressure level at 100 feet would’ve been about 120 decibels.

According to The American Academy of Audiology, ambulance and fire engine sirens measure 130 decibels and fireworks and custom car stereos measure 140 decibels.

Hearing damage is a factor of exposure time, frequency and intensity of the sound/audio broadcast. OSHA allows noise exposure to 115 decibels for up to 15 minutes per day, just 5 decibels lower than what Ms. Piper may have been exposed to for seconds.

While LRAD broadcast levels are purposely kept below the threshold that could cause permanent hearing damage from instantaneous exposure, when activated at close range, most people experience audible discomfort and quickly cover their ears and move away.  

Just the act of covering the ears with hands reduces the sound pressure level by approximately 25 decibels. By covering her ears, the maximum level Ms. Piper would have been exposed to would have been approximately 95 decibels, 15 decibels less than what concert attendees willingly listen to for hours at rock concerts.

Commenting on LRAD’s use at the Pittsburgh G20 Summit, Jon Stewart lampooned the supposed harmful effect of LRAD’s alarm tone on "The Daily Show with Jon Stewart" by putting his fingers in his ears.

Ms. Piper also seems to have confused some of her symptoms with exposure to intense infrasound (frequencies below 20 hertz).

Intense infrasound can be felt throughout the body and can cause nausea and dizziness. With its frequency range of 200 hertz to 10,000 hertz, LRAD is incapable of broadcasting infrasound.

If Ms. Piper experienced the temporary or permanent conditions cited in her quotes, then individuals who find themselves in close proximity to fire and police sirens at full volume or those who willingly subject themselves to hours of loud music at rock concerts or listening to their custom car stereos should be suffering more intensely from the same symptoms and conditions Ms. Piper described.

LRAD is not a weapon. It is an effective long-range communications system used to clearly broadcast critical information, instructions and warnings.

LRAD broadcasts are far superior to bullhorns, allowing law enforcement to communicate clearly to large gatherings from safe distances in outdoor venues.

While LRAD can broadcast very loudly, law enforcement personnel are trained on the proper use of the device and have full control of the audio output through a prominently positioned volume control knob.

Unlike tear gas, Tasers, rubber bullets, pepper spray and flash bang grenades (which emit an instantaneous burst of up to 175 decibels), LRAD voice and alarm tone broadcasts can be modulated in response to protesters' actions.

In closing, we note that 190 arrests were made in connection with the Pittsburgh G20 Summit, where LRAD systems were utilized versus more than 1,100 arrests reported from last summer’s Toronto G20 Summit where LRADs were available but not deployed.

In these difficult situations, LRAD has proved to be very effective in assisting law enforcement communicate their instructions to large, unruly crowds and resolve uncertain situations with minimal property damage and fewer arrests.

Robert Putnam is in media relations with the LRAD Corp.

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Karen Piper October 14, 2011 | 2:01 p.m.

I would encourage Mr. Putnam to prove he is right by standing 100 feet from an LRAD projecting sound at 149 decibels for three minutes and having a hearing test before and after. I would even pay for his tests, and he could prove that the LRAD was harmless. In fact the Seoul Metropolitan Police did a similar a test, though only exposing people for a few seconds. Reporters found that "Even a five-second exposure to the warning siren, which repeatedly whistles fast, gives feelings of numbness in the eardrums and queasiness. . . One could feel his or her head beating and vibrating when exposed to warning sirens of 116 decibels at 32 meters away. A person would find it hard to endure the sound even at a distance of 100 meters. After the demonstration ended, reporters at the scene complained of nausea."

It also apparently did not occur to Mr. Putnam that you may not be able to plug your ears when your hands are full.

A simple search of the Physicians Reference Desk (PRD) shows that permanent hearing loss occurs with "exposure to noise louder than 110 decibels . . . for more than one minute."

It appears that Mr. Putnam's letter merely demonstrates that my hearing loss was indeed caused by the LRAD.

Karen Piper, Professor

(Report Comment)
Ricky Gurley October 14, 2011 | 2:47 p.m.

"Sound pressure is measured in decibels (dB). Like a temperature scale, the decibel scale goes below zero. The average person can hear sounds down to about 0 dB, the level of rustling leaves. Some people with very good hearing can hear sounds down to -15 dB. If a sound reaches 85 dB or stronger, it can cause permanent damage to your hearing. The amount of time you listen to a sound affects how much damage it will cause. The quieter the sound, the longer you can listen to it safely. If the sound is very quiet, it will not cause damage even if you listen to it for a very long time; however, exposure to some common sounds can cause permanent damage. With extended exposure, noises that reach a decibel level of 85 can cause permanent damage to the hair cells in the inner ear, leading to hearing loss. Many common sounds may be louder than you think"…

Environmental Noise

Weakest sound heard 0dB
Whisper Quiet Library 30dB
Normal conversation (3-5') 60-70dB
Telephone dial tone 80dB
City Traffic (inside car) 85dB
Train whistle at 500', Truck Traffic 90dB
Subway train at 200' 95dB

***Level at which sustained exposure may result in hearing loss 90 - 95dB***
Power mower at 3' 107dB
Snowmobile, Motorcycle 100dB
Power saw at 3' 110dB
Sandblasting, Loud Rock Concert 115dB

***Pain begins 125dB***
Pneumatic riveter at 4' 125dB
Even short term exposure can cause permanent damage - Loudest recommended exposure WITH hearing protection 140dB
Jet engine at 100', Gun Blast 140dB

***Death of hearing tissue 180dB***

***Loudest sound possible 194dB***

Mr. Putham must either currently be a Law Enforcement Officer or at one time was a Law Enforcement Officer?

Be sure to delete that.....

(Report Comment)
Aaron Rogier October 19, 2011 | 8:20 p.m.

The following was posted to the Maneater in part.

From what I understand and engineers may correct me, but the inverse square law applies to radiation sources that radiate in all directions. Notably lasers as unidirectional radiators, and as such are not subject to the inverse square law in the same way that unfocused radiation sources are. From what I understand the motivation for LRAD communication devices is maintaining integrity of an audible message over distances that are not possible with traditional audio sources. While LRAD may not be able to achieve the efficiency of a laser in directing audible sounds, but it is going to be a more focused than the unfocused source the inverse square law considers.

With that said here I do ask to what extent the inverse square law's effect on a laser may have on an LRAD device.

As a more serious note, of what relevance is the number of arrests at one location having to do with protests having to do with a different situation in a different city. You aren't dealing with different limits of human fatigue, but you do have to content with the fact that Toronto and Pittsburgh are going to have different people attending protests. Measuring the raw number of arrests between jurisdictions in two different sovereign nations is as meaningless as metrics come.

Consider that for many people what you advertise as the maximum tolerable sound level may be deafening for many. When food producers have to warn customers who may have food allergies of potential adverse interactions to wheat proteins, how or why should producers of tools a general population may be exposed to be held to a lower standard. You sell a device that involuntarily projects acoustic waves towards an audience, working around the potential adverse reactions of the least vulnerable rather than the most vulnerable is despicable.

(Report Comment)

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