Miscellaneous Acoustics Projects
An exploration of the Helmholtz resonator using finite element to
visualize sound waves
- Helmholtz resonators are used to control noise propagating down
pipes and ducts
- Adding the resonator affects the system, and can make the problem
worse at off-target frequencies
- Begin the story here
- Learn more about the software at Comsol, Inc.
Critical Bands demo for "Introduction to Acoustics" by Daniel
- Aural version of a figure in Russell's text
- Demonstrates critical bands and beating through sine tones
- Created with significant work by Brad Roche, a student in
- Read the description and hear the .wav file here
Microflown Sensors deployed in a new Input Impedance head for
The Microflown sensor is mounted inside this 1/2"
probe, along with a precision microphone.
- Read the proposal
- Check out the sensors
-- a radically new way to incorporate
particle velocity measurements
- A quick
description of the equipment, a new arrival in the lab
Simple piezoelectric element and lavalier measures Input
for less than $20...
- Piezo disc from a Radio Shack buzzer fixed to a PVC coupler
- Voltage applied to the piezo disc causes it to flex, creating
- A lavalier electret microphone (also from Radio Shack) near
piezo disc, measures pressure.
- Volume velocity is related to the voltage applied to the disc
through a calibration function.
- The ratio of pressure over volume velocity is input impedance.
- Student help driving the project came from Tim Swieter, 2003
Chidi Uhiara, 2004. Both are Acoustics minors.
- Based on: A. H. Benade and M. I. Ibisi, "Survey of impedance
methods and a new piezo-disk-driven impedance head for air columns," J.
Acoust. Soc. Am. 81, 1152-1167
End Correction for varied flange and pipe sizes
- A standing wave in a pipe depends on the boundary conditions
each end of the tube.
- A closed end has a pressure maximum, but the pressure minimum
an open end is just beyond the tube.
- The end correction is the difference between the location of
pressure minimum and the actual end of the tube.
- The end correction depends on the type of open end - flanges
different sizes influence the end correction.
- The "acoustical length" of the tube is related to its
- By measuring the resonance frequencies, we calculate the end
correction as a function of pipe radius and flange size.
- Student Brandon Dilworth, 2004 (Acoustics minor) accomplished
much of the work on this project.
Binaural Localization studies with the HEAD mannekin
- The mannekin incorporates the effects of the head and torso
sound entering precision microphones inside the ears.
- Impulse sounds were recorded at various azimuthal positions
horizontal circle around the head.
- The right- and left-ear signals were processed in Matlab and
CoolEdit to observe how we localize sound via:
- interaural time difference
- interaural level difference
- anatomical transfer function filter characteristics
- Jason Kolenda, 2002 and Kim Pregitzer, 2002 worked on this
project as part of their coursework in Acoustics.