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The Journal of the Acoustical Society of America
Article . 1982 . Peer-reviewed
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Impedance and impulse response measurements using low-cost components

Authors: M. I. Ibisi; A. H. Benade;

Impedance and impulse response measurements using low-cost components

Abstract

A thin 27-mm-o.d. disk transducer (from Radio Shack 273-060 signaler) is RTV sealed to the end of a measurement tube whose 15 mm i.d. not only approximates the transducer disk's nodal circle but also the i.d. of a clarinet, sax, or trumpet mouthpiece. A 10-mm-o.d. electret microphone element (Radio Shack 270-092) mounted through the tube wall near the piezo driver picks up the resulting pressure signal. When the high mechanical impedance driver is excited by a sinusoidal sweep via a 6-dB/oct integrator, the resulting pressure signal gives an excellent view of the input impedance of the air column over the musically useful range to 3.5 kHz since the driver resonance is at ω0/2π≃5 kHz and bandwidth g≃ω0/6. A ramplike drive voltage (running between op-amp supply limits) of the form A (1 − e−gt/2) for θ⩽t⩽2π/ω0, and constant thereafter, gives a clean pressure pulse ≃ const.(1 − cos ω0t) whose FWHM≃0.1 ms is convenient for impulse response studies. Drive signal spectrum, piezoelectric coupling, and driver-to-tube coupling each minimize transducer second-mode ringing effects. Driver-to-mike proximity effects are small, visible, calculable, and easily allowed for in both impulse and sinusoidal drive usage. The driver is not quite rigid, perturbing the air column slightly, but corrections are straightforward. Applications for research and in teaching labs will be described. [Assisted by NSF.]

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
3
Average
Average
Average
bronze