Vortex sound in bass-reflex ports of loudspeakers : part 1. observation of response to harmonic excitation and remedial measures

N.B. Roozen, M. Bockholts, P. van Eck, A. Hirschberg

Research output: Contribution to journalArticleAcademicpeer-review

16 Citations (Scopus)
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Abstract

At high sound pressure levels a bass-reflex port produces blowing sounds, especially in the case of small loudspeaker boxes with narrow bass-reflex ports. The blowing sounds are caused by vortex shedding of the acoustic flow at the end of the port at high flow velocities. It has been found that acoustic standing waves in the longitudinal direction of the port are excited in a pulsatile manner by the periodically generated vortices. This is demonstrated by time history measurements of the blowing sounds of a loudspeaker system with a bass-reflex port driven by a harmonic signal. Broadband turbulence sound appears to be weaker than these deterministic sounds. It has been found that, near the 1-kHz port resonance frequency, the power level of the blowing sounds can be reduced by 8 dB by using a port cross section that diverges gradually toward both port ends with a slope angle at the port ends of about 6°, and rounding the edges at both port ends. © 1998 Acoustical Society of America.
Original languageEnglish
Pages (from-to)1914-1918
Number of pages5
JournalJournal of the Acoustical Society of America
Volume104
Issue number4
DOIs
Publication statusPublished - 1998

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