Apparatus for analyzing complex acoustic fields within a duct
US4144768A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 3, 1978 |
| Grant date | Mar 20, 1979 |
| Priority date | — |
| Expiry date | Jan 3, 1998 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2291/02872
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A system for resolving a complex acoustic field, resulting when acoustic energy propagates through a duct, into component unit spatial pressure patterns or modes is disclosed. In each disclosed system arrangement, an acoustic filter, which includes one or more annular cavities, circumferentially surrounds the duct through which the acoustic energy propagates and sound is coupled from the duct into one end of each annular filter cavity via a series of openings which exhibit a relatively high acoustic impedance and a relatively high resistance to fluid flow. Each filter cavity is dimensioned such that it is excited into resonance when the circumferential distance between adjacent nodes of a modal component of the pressure pattern within the duct is mathematically related to the velocity of sound within a filter cavity by a predetermined factor. When a cavity resonates, maximum acoustic pressure transfer occurs between the duct and two or more microphones that are circumferentially spaced apart from one another along the second end of each annular filter cavity. A gas mixture is introduced into the annular cavities to control the velocity of sound within the cavities and the compositi…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.