PUBLIC SPEAKER
Curiosity Questions
• Most mammals have binaural (two-ear) hearing. How does where we stand in relation to a sound affect
how we hear that sound in our left and right ears? Why would ear positioning be helpful in the wild?
• In the past, people gathered as a group to listen to radio and music was done as a group. Now that we listen to music and programs
alone, often through headphones, How do you think the perception of sound and the experience of listening are different?
• Can you use your voice to make high and low sounds? Loud and soft? Rough and smooth?
• What happens when you make those sounds through the Public Speaker? Can you think of
other ways to amplify sound?
Science Themes
Sounds are the result of vibrations, transmitted as waves. The object that makes the sound makes tiny,
rhythmic back-and-forth movements (vibrations), and those movements create rhythmic ripples (waves)
in the stuff between the source and the listener (the medium).
Sound travels most slowly through air and other gases, and most rapidly through solids, like rocks and metals.
For instance, sound travels through air a 342.2 metres per second; through iron at over 5000 metres per second; and through
diamond at 12000 meters per second.
For perspective, the average car travels on a highway at 33.3 m/second, about ten times slower than sound through air. Sound
cannot travel through outer space since space is a vacuum. There’s no medium -- no stuff -- to carry the sound waves from the
vibrating source to a listening ear.
33.3 m/second
PUBLIC SPEAKER
Science Themes
The speed of the vibration determines a sound’s pitch: fast vibrations make high tones and slow
vibrations make low tones. A sound is also characterized by its volume (loud or soft tones), and
sound quality (roughness or smoothness).
Speaking and listening are very complex activities. Humans can adjust their voices, changing
how they formulate sounds for different tasks, such as shouting, whispering, or giving a speech.
Amazing physiological actions take place for the human ear to perceive vibrations as audible
sounds within a fraction of a second.
To hear a sound, the ears act like machines and the brain acts like a computer. Sound waves enter the ear through the eardrum, which
then amplifies, or loudens, these vibrations in the middle part of the ear. In the inner ear, sound vibrations cause sensitive nerve
endings to vibrate, and these vibrations are converted to electrical signals that the brain interprets.
A loudspeaker amplifies sound by combining back-and-forth movements and electromagnetic current. As you turn up the volume on
your stereo, you can see this back-and-forth vibration in the cone of the speaker.
PUBLIC SPEAKER
Makers and Making
PUBLIC SPEAKER | “Public Speaker” refers to both the person doing the speaking and the device amplifying the sound. It is a working
wooden speaker box, created by Holly Simon and first showcased at the Royal Architecture Institute of Canada (RAIC) Festival of
Architecture. It was designed to project live audio of the festival to people on the street, as a means of teaching people about
architecture and encouraging people to speak to each other. Talk about changing what the community hears!
Measuring in at over 227 kilograms (almost 500 pounds), standing roughly 2 metres high, the Public Speaker is made of fibre-reinforced
plastic with a lightweight aluminum frame. The mouthpiece will be illuminated with LED lights to stand out at night.
Sources
How does sound in air differ from sound in water? http://www.dosits.org/science/soundsinthesea/airwater
American Dictionary of Sound: http://web.archive.org/web/20080625012016/http://www.bartleby.com/61/65/S0576500.html)
Department of Neurophysics – University of Wisconsin: http://www.neurophys.wisc.edu/h&b/textbook/sound_transmission.html)
Wikipedia – speed of sound, acoustics:
http://ocw.mit.edu/high-school/engineering/guitar-building/physics-of-the-guitar/force-and-torque-distribution/