Audio dosimeter

• US 4,554,639 A
• Filed: 04/06/1983
• Issued: 11/19/1985
• Est. Priority Date: 04/06/1983
• Status: Expired due to Term

• Current Assignee: EMA Corp. (Ametek Incorporated)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Betsill, Harry E., Baker, William B.
• Primary Examiner(s): Wise, Edward J.
• Application Number:
  US06/482,594
• Time in Patent Office: 958 Days
• Field of Search: 364/556, 364/557, 364/571, 73/648, 73/645, 73/646, 73/632, 73/647, 179/1.1
• US Class Current: 702/1
• CPC Class Codes: G01H 3/14 Measuring mean amplitude; Measuring mean power; Measuring time integral of power

Abstract

An audio dosimeter for use by an individual for measuring exposure to sound which contains the following components:

(a) an electronic microphonic sound sensor means,

(b) an amplifier and weighting circuit,

(c) an x-squared detector circuit,

(d) a temperature compensation circuit;

(e) analog to digital time converter,

(f) a microcomputer which controls functions of the temperature compensator circuit and analog to digital time converter and has unique logarithmic mathematics for converting the signal from the converter into sound measurement values such as percent of dose, average and maximum decibel levels and instantaneous sound level.

Claims

1. An audio dosimeter for measuring exposure to sound comprising:

(a) an electronic microphonic sound sensor means which generates electric input signal upon activation by sound;

(b) an amplifier and weighting circuit electrically connected to the sound sensor means which amplifies the input signal from the sound sensor means and provides an "A" weighted signal directly related to the frequency of the sound which activated the sound sensor;

(c) an x-squared detector circuit electrically connected to the amplifier and weighting circuit which receives the input signal and generates a voltage signal which is proportional to the log of the square of the input signal;

(d) temperature compensation circuit electrically connected to the x-squared detector circuit which develops reference signals through ramping and intergrating means matched to the x-squared detector circuit and thereby temperature compensating the voltage signal of the x-squared detector circuit;

(e) analog to digital time converter circuit electrically attached to the temperature compensation circuit which converts the temperature compensated voltage signal to digital time signal;

(f) a microcomputer electrically connected to the temperature compensation circuit and controls the integrating and ramping functions of the circuit and electrically connected to the analog to digital time converter and controls the functions of the converter and receives the digital time signals from the converter and having a calculating means for converting the time signals into sound measurement values.

2. The audio dosimeter of claim 1 having a gain circuit electrically connected to the amplifier and weighting circuit and microcomputer which allows selection of additional amplifier gain for audio range.

3. The audio dosimeter of claim 2 having a parameter switch electrically connected to the microcomputer for selection of doubling rates, threshold levels and criterion levels.

4. The audio dosimeter of claim 1 in which the x-squared detector circuit comprises a bilateral logging circuit, a bilateral antilogging and integrating circuit wherein the input signal is converted to a bilateral current signal and develops a voltage which is proportional to two times the log of the input signal and is fed into the bilateral antilogging and integrating circuit producing a voltage which is proportional to the log of the square of the input signal.

5. The audio dosimeter of claim 1 in which the temperature compensation circuit having constant current source and a capacitor connected in parallel comprises:

(a) a logging voltage to current converter, and a first antilogging converter feeding the constant current source thereby generating a low reference signal;

(b) a second antilogging converter feeding the parallel connected capacitor and constant current source thereby generating a first ramping reference signal;

wherein both the low reference signal and the ramping reference signal being compensated for temperature and where the circuit produces a momentary high reference signal across the capacitor upon a command from the microcomputer to start the ramping reference signal ramping down;

(c) a first comparator which receives the low reference signal and the ramping reference signals and detects end-of-ramp;

(d) a second comparator which receives the signals of (c) above and the input signal from the x-squared detector and determines when the ramping signals intersect the input signal;

wherein a signal from the first or second comparator fed to the logic circuit of the microcomputer pulls down the interrupt line of the microcomputer and the microcomputer which controls ramping functions ratios time intervals in the ramping functions and detects sound pressure levels in decibels.

6. The audio dosimeter of claim 1 having a display electrically connected to the computer to visually show sound measurement values determined by the microcomputer.

7. The audio dosimeter of claim 6 in which the microcomputer has a program for calculating values of percentage dose, average decibel level of exposure, maximum decibel level of exposure, instantaneous sound level and time of exposure.

8. The audio dosimeter of claim 7 containing a selector switch which allows for the display of the individual values and allows the dosimeter to be used as a sound level meter by display of instantaneous sound level.

9. The audio dosimeter of claim 1 having a control, interface connected to the microcomputer for sending data to a second computer.

10. A true x-squared detector circuit which receives an input signal and determines the x-squared value of the signal;

wherein the circuit comprises;

(a) an x-squared detector circuit which receives the input signal and generates a voltage signal which is proportional to the log of the square of the input signal;

(b) temperature compensation circuit electrically connected to the x-squared detector circuit which develops a reference signal through ramping and integrating means matched to the x-squared detector thereby temperature compensating the voltage signal of the x-squared detector circuit;

(c) analog to digital time converter circuit electrically attached to the temperature compensation circuit which converts the temperature compensated logging voltage signal to digital time signal;

(d) a microcomputer electrically connected to the temperature compensation circuit and controls the integrating and ramping functions of the circuit and electrically connected to the analog to digital time converter and controls the functions of the converter and receives the digital time signal from the converter and having a calculating means for converting the time signal into x-squared value of the input signal.