DEVICE FOR MEASURING ACOUSTIC QUANTITIES

• US 3,658,147 A
• Filed: 06/29/1970
• Issued: 04/25/1972
• Est. Priority Date: 06/29/1970
• Status: Expired due to Term

• Current Assignee: Louis T. Ho, Robert J. Flaherty III
• Original Assignee: Louis T. Ho, Robert J. Flaherty III
• Inventors: Ho, Louis T., Flaherty, Robert J. III
• Primary Examiner(s): Borchelt, Benjamin A.
• Assistant Examiner(s): Moskowitz, N.
• Application Number:
  US05/050,767
• Time in Patent Office: 666 Days
• Field of Search: 181/.5AP
• US Class Current: 73/647
• CPC Class Codes: G01N 2291/02818 Density, viscosity
• CPC Class Codes: G01N 2291/02872 Pressure
• CPC Class Codes: G01N 29/02 Analysing fluids using acoustic emission techniques G01N29/14 ; constructional or flow details for analysing fluids G01N29/222; optoacoustic fluid cells G01N29/2425

Abstract

A device for measuring and displaying four different acoustic quantities in a fluid medium. The specific acoustic quantities are: acoustic pressure; particle acceleration; acoustic impedance; and acoustic power density. All of these quantities are determined simultaneously and each is instantly displayed as a function of the driving frequency of an excitation source in the fluid medium.

Claims

1. A method for determining certain acoustic characteristics of a fluid medium instantly and simultaneously comprising:

oscillating an acoustic source positioned in said medium at a predetermined frequency;

sensing the pressure produced by said acoustic source at two points A and B in said medium separated by a small distance;

producing output voltages eA and eB related to said sensed pressures at points A and B respectively;

summing said voltages eA and eB and thereby producing output voltage (eA + eB);

differencing said voltages eA and eB and thereby producing output voltage (eA - eB);

converting said voltages (eA + eB) and ( eA - eB) separately to d.c. logarithmic equivalent voltages log (eA+ eB) and log (ea eB) respectively;

displaying voltages log (eA + eB) and log (eA - eB) separately as functions of said oscillating acoustic source frequency and thereby producing simultaneous displays of acoustic pressure and particle acceleration, respectively;

producing a voltage eF related to the frequency of said oscillating acoustic source;

converting said voltage eF to a d.c. logrithmic equivalent voltage log eF;

applying said voltages log eF , log (eA + eB) and log (eA - eB) as inputs to a first d.c. sum and difference network in a manner whereby output voltage log is produced;

applying the voltages (eA + eB) and (eA - eB) as inputs to a phasemeter thereby producing an output voltage e phi related to the phase angle difference between these voltages; and

displaying the voltages log and e phi separately as functions of said oscillating acoustic source frequency and thereby producing simultaneously with said displays of acoustic pressure and particle acceleration, displays of the magnitude of acoustic impedance and the acoustic impedance phase angle.

2. The method of determining certain acoustic characteristics of a fluid medium as recited in claim 1, further comprising the steps of:

applying said voltages log ef, log (eA+eB) and log (eA-eB) as inputs to a second d.c. sum and difference network in a manner whereby output voltage log is produced; and

displaying said voltage log as a function of said oscillating acoustic source frequency and thereby producing simultaneously with said displays of acoustic pressure, particle acceleration, acoustic impedance magnitude and acoustic impedance phase angle a display of acoustic power density.

3. A device for measuring and displaying different acoustic characteristics of a fluid medium, comprising:

an acoustic excitation source for producing standard acoustic signals in said fluid medium at a predetermined driving frequency;

an oscillator connected to said excitation source for driving said source at said predetermined driving frequency;

a dual sensor hydrophone positioned in said fluid medium for determining the pressure produced by said oscillating acousTic source;

a first amplifier connected to one of said pressure sensors and a second amplifier connected to the other pressure sensor;

a summing amplifier connected to both said first and second amplifiers;

a differencing amplifier connected to both said first and second amplifiers;

first and second log converters connected to said summing and differencing amplifiers respectfully; and

a first display means connected to said first log converter, said second log converter and said oscillator for displaying acoustic pressure and particle acceleration as functions of said driving frequency simultaneously.

4. A device for measuring and displaying different acoustic characteristics of a fluid medium as recited in claim 3, further comprising:

a third log converter connected to said oscillator;

a first d.c. sum and difference network containing three input terminals, said third log converter connected to said first input terminal, said first log converter connected to said second input terminal and said second log converter connected to said third input terminal;

a phasemeter connected to both said summing amplifier and said differencing amplifier; and

a second display means connected to said first d.c. sum and difference network, said phasemeter and said oscillator for displaying acoustic impedance magnitude an acoustic impedance and angle as functions of said driving frequency simultaneously with each other and with said displays of acoustic pressure and particle acceleration.

5. A device for measuring and displaying difference acoustic characteristics of a fluid medium as recited in claim 4, further comprising;

a second d.c. sum and difference network substantially the same as said first network and containing three input terminals, said second log converter connected to said first input terminal, said first log converter connected to said second input terminal and said third log converter connected to said third input terminal; and

a third display means connected to both said second d.c. sum and difference network and said oscillator for displaying acoustic power density as a function of said driving frequency simultaneously with said displays of acoustic pressure, particle acceleration, acoustic impedance magnitude and acoustic impedance phase angle.