The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 29, 1987
Filed:
Jul. 28, 1986
Erling Frederiksen, Holte, DK;
Aktieselskabet Bruel & Kajaer, Naerum, DK;
Abstract
An acoustic calibration device for intensity measuring systems comprising at least two pressure microphones to be calibrated without using an anechoic chamber. The calibration device comprises at least two cavities interconnected by means of one or several acoustic resistance elements. One of the pressure microphones is to be inserted into one of the cavities and the second pressure microphones is to be inserted into the second cavities. A sound source is connected to one of the cavities. In connection with the subsequent cavity the acoustic resistance thus forms an acoustic RC-link providing a phase shift proportional to the frequency corresponding to the conditions in the free field. By a suitable dimensioning of the RC-link a phase shift corresponds to the phase shift over a distance of e.g. 50 mm in the free field. The sound source is able to generate either white noise or pink noise depending on whether measurements are performed over fixed frequency intervals or relative frequency intervals.