The speed of sound in air at 20o C is 344 m/s. (a) What is the wavelength of a sound wave with a frequency of 784 Hz, corresponding to the note G5 on a piano, and how many milliseconds does each vibration take? (b) What is the wavelength of a sound wave one octave higher (twice the frequency) than the note in part (a)?
9/7/2016 3.3 Hearing What do we hear Sound waves: vibrations of air o Just like we don’t see all the possible wavelengths of light out there, we also don’t hear all the frequencies of possible sound waves. o We hear between 2020,000 Hz (cycles per second) Features of sound 1. Pitch (low, high, medium tone) o Corresponds to frequency o Long wavelength, low frequency o Short wavelength, high frequency 2. Loudness (how loud is it) o Corresponds to amplitude 3. Timbre (what is the quality of the sound) o Corresponds to the purity of the wavelengths (how many different frequencies are there Similar to light) Light Sound Wavelength Hue (color) Pitch Amplitude Brightness Loudness Purity Saturation Timbre We measure in decibels (dB). o Ex: Absolute threshold (0), Whispering (20dB), Rainfall (50dB), Normal conversation (60dB), Hair dryer (70dB) o Ex: Average city traffic (80dB), Motorcycle that is 25 feet away (88dB), MP3 Player at max volume (105dB), Snowmobile (105dB) o Ex: Jet engine (140dB) o Continual exposure may cause damage (>80dB) o Hearing becomes painful (> 125dB) Ear Transforming Sound Waves into the Language of the Brain Ears transduce the physical motion of sound waves into the electrical and chemical signals of the nervou
