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Browse Prior Art Database

Acoustical Noise Versus Time Analysis

IP.com Disclosure Number: IPCOM000094434D
Original Publication Date: 1965-Jan-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Peterson, RH: AUTHOR

Abstract

Procedures for measuring rms sound pressure level and objectionability NR on a time scale can be very cumbersome for high cyclic rates and low audio frequencies. Here, to achieve this measurement, any particular sound source is cyclically attenuated for a short increment of time. The remaining sound level is sensed or measured while the attenuated sound level is swept through the cycle.

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Acoustical Noise Versus Time Analysis

Procedures for measuring rms sound pressure level and objectionability NR on a time scale can be very cumbersome for high cyclic rates and low audio frequencies. Here, to achieve this measurement, any particular sound source is cyclically attenuated for a short increment of time. The remaining sound level is sensed or measured while the attenuated sound level is swept through the cycle.

Oscilloscope 10 is synchronized with the noise source which is considered to be cyclic. In this example, consider the noise source to be a machine having many moving parts which are operated at different times within a cycle. However, from a machine timing diagram, it is possible to determine the period of operation for any one of the moving parts. Terminal 11 is connected to a cyclic trigger, not shown. The cyclic trigger can be set during any portion of the machine cycle.

With the cycle trigger set, oscilloscope 10 produces an output signal which operates electronic switch 12. Switch 12 shorts out attenuator 13 except during the selected Delta T time as determined by the delayed sweep of oscilloscope
10. The signal for operating switch 12 can also be used to fire a strobe trigger, not shown, to permit observation of the operating noise source. The remaining sound level is analyzed by acoustical analyzer 20.

The output from each filter section of 20 is attenuated independently in proportion to the known objectionability of each octave. The rm...