1. Mechanical & Manufacturing
Engineering
Ollscoil Chaithair Bhaile Atha Cliath
Dublin City University
Photoacoustic Cell
Laser
Transmitter
Laser Receiver
Unit
Potentiometer
Volume Control
“Surface Displacement
Amplitude”
BNC Connector
Signal Output
Reflected Laser Beam
2. WINDOW
STIMULATOR:
A piece of glass is
attached to the
centre of the speaker
cone mimicking a
real world vibrating
window surface.
4. LASER RECEIVER CIRCUIT:
Amplitude modulation of the laser beam
deflection caused by the displacement of the
vibrating glass surface of the photoacoustic
chamber is deciphered and amplified into an
audible audio signal.
Real World Application
Designed Laser Microphone using
the “angular grazing method” for
photoacoustic signal detection.
DESIGN OF A LASER MICROPHONE
FOR PHOTOACOUSTIC SIGNAL DETECTION ABIOLA OGUNDE
1. LASER
TRANSMITTER:
Class II 1mW
laser diode (650
nm wavelength)
used as the light
source. Laser
beam is bounced
off a vibrating
glass surface.
LASER MICROPHONE OPERATION:
Detects displacement-amplitudes (vibrations) on a reflective glass
surface with a laser beam and converts the deflected motion of
the beam into a digital signal using a laser receiver unit.
3. PHOTOACOUSTIC CHAMBER:
A sound source (speaker) is enclosed in
a photoacoustic cell and sealed with a
glass on the top. This is will result in
the displacement-amplitude of the
glass surface.
PROJECT OBJECTIVE!
Non-destructive
method of
photoacoustic signal
detection USING A
LASER MICROPHONE.
PA Detection Results
Blue waveform: 2Hz Sine Wave sound frequency sent to the speaker in the PA chamber speaker.
Black waveform: Detected 2Hz frequency sound signal with noise.