Sound Tech Report

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Arch 498C - Responsive Environments
Tech Report — Sensing Sound
Doaa Alsharif | Dana Lee | Virginia Bradbury
SOUND IN GENERAL
Sounds are waves of pressure formed from mechanical vibrations traveling through a medium
of liquid, solid or gas. These pressure can be produced by any vibrating objects. When these
vibrations hit our ears a specific nerve cells are stimulated to pass electrical signals to the
brain which will cause the experience of hearing. Wavelength, frequency, and velocity are the
characteristics that defines sound.
Sound Sensors:
Sound sensors sense any audible or inaudible sounds to human ears. They are detected
through microphones or specialized transceivers. The challenges for these sensors is to
separate meaningful sounds from inconsequential sounds.
Sound Detector:
SparkFun sound detector is an audio sensing board with
three different outputs. The Sound Detector not only
provides an audio output, but also a binary indication of the
presence of sound, and an analog representation of its
amplitude. The 3 outputs are simultaneous and
independent, so you can use as many or as few as you want
at once. It costs $10.95 at SparkFun $7.95 at AdaFruit.
Voice Recognition:
EasyVR 3.0 is a multi-purpose speech recognition
module designed to add versatile, robust and cost
effective speech and voice recognition capabilities to
virtually any application. It costs $49.95.
HYDROPHONES
Hydrophones are devices that can detect underwater sounds through the use of piezoelectric
transducers, which produce electric current when a mechanical force is applied. Because the
transducers change their shape when a force (like a sound wave) is applied, they can convert
the produced energy into electric current when a sound is detected.
Advantages:
- Waterproof
- Do not require a power source
- Inexpensive
- Very accurate
- Ranges up to 50 miles
Disadvantages:
- Cannot distinguish between multiple objects
- Cannot distinguish between natural vs. artificial noise
- Needs another device to detect, record, or transmit the findings
Circuitry:
MICROPHONES
Thinking about bending and sound, instruments are a great example of that. For example,
wind instruments that use a reed, rely on the bending back and forth of a reed when they
blow into the mouth piece to create tones by using that vibration. In our modern day, we
even have electronic wind instruments, aka wind synthesizers/wind controllers. Although they
are played like a normal wind instrument, no sound is actually produced. They usually use
breath as volume control. Converts electrical signals to a synthesizer that converts the signals
into audio signals that can be played through speakers.
Applications:
Most devices that sense sound use a microphone of some type. For example, a clap on/off
flight looks for a sudden, short, strong sound. The controller can be set to trigger if the sound
is higher than a normal set threshold. Microphone are transducers that sense and convert
sound waves into electrical energy using a diaphragm, where the sound waves bend the
diaphragm. Speakers also work in a similar way.
Microphones detect that by allowing a diaphragm to move, which causes other components
in the microphone to vibrate. These vibrations are converted into an electrical current which
becomes the audio signal.. How? Early mics compressed graphite powder (I think) which
changed resistance within the powder, and we can measure voltage change with the
Arduino....
References:
http://www.electronics-tutorials.ws/io/io_8.html
https://www.sparkfun.com/products/12642
http://www.tech-faq.com/hydrophone.html
http://www.fleetsubmarine.com/sonar.html
http://www.exfac.com/aussie_bray/hydro_circuits.htm
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