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Method to Provide Electronic Ear Protection

IP.com Disclosure Number: IPCOM000040411D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 3 page(s) / 31K

Publishing Venue

IBM

Related People

Linton, RL: AUTHOR [+2]

Abstract

A method is described which protects the hearing of an individual while allowing normal sound levels to be heard. Earplugs or earphones that muffle loud noises to prevent hearing loss muffle not only the loud noises but also the softer ones, such as conversation. This problem can be solved by designing the earphones to pass all acoustic levels below a set value and limiting all those above that value. The equipment required consists of: 1. A microphone. 2. An amplifier circuit with the following properties: a. Unit gain for all signal magnitudes below a set value. b. Clipping to prevent the magnitude from exceeding the set value. 3. A speaker to transmit the sound to the user's ear. The clipping level is set by turning a knob.

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Method to Provide Electronic Ear Protection

A method is described which protects the hearing of an individual while allowing normal sound levels to be heard. Earplugs or earphones that muffle loud noises to prevent hearing loss muffle not only the loud noises but also the softer ones, such as conversation. This problem can be solved by designing the earphones to pass all acoustic levels below a set value and limiting all those above that value. The equipment required consists of: 1. A microphone.

2. An amplifier circuit with the following

properties:

a. Unit gain for all signal magnitudes below a

set value.

b. Clipping to prevent the magnitude from

exceeding the set value.

3. A speaker to transmit the sound to the user's ear.

The clipping level is set by turning a knob.

An implementation of the device is shown in the figure.

The function of the blocks, shown in the figure, is as

follows:

INPUT TRANSDUCER:

The input transducer consists of a simple microphone

element which has a dynamic frequency response which is

flat over the desired bandwidth of the device.

The bandpass amplifier serves to raise the signal level

output of the input transducer to a suitable level

while limiting its output to the frequency range

desired.

ANALOG DELAY:

The analog delay compensates for any process delays in

the rectifier and filter stage, limit detector stage,

and the gain-controlled amplifier stage in order to

prevent momentary passage of a signal of step or

impulse nature. Delay would be small enough to be

imperceivable to the wearer.

GAIN-CONTROLLED AMPLIFER:

This amplifier has a gain figure inversely proportional

to the magnitude of its control input. Thus, a larger

control voltage input reduces the amplifier's gain.

RECTIFIER and FILTER:

This stage outputs a DC voltage from the amplified AC

input voltage. The output is proportional to the peak

amplitude of the input signal.

LIMIT DETECTOR:

The li...