PHYS 1240 Lecture Notes - Lecture 8: Sound Intensity, Spectral Density, Logarithmic Scale
9 Nov 2018
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Document Summary
Spatial interference- destructive interference if the distance from the two sources lambda/2 apart. Timbre is the unique sound of a steady tone which depends on the frequency spectra. Spectrogram or sonogram - intensity as function of both frequency and time. Frequency spectrum - intensity as a function of frequency (shows how much energy or power there is in a specific frequency range. If the lines are wavy, the pitch is changing. Proportional to the square of the pressure amplitude. Contains a logarithmic scale, so a 10 db increase is a 10 fold increase in intensity. A 20 db increase is two increases of 10 db. A 40 db increase in sound level corresponds to a 10,000 fold increase in intensity. Even if the fundamental frequencies are removed, the human brain can fill it in. Formula for sound intensity level sil (db) = 10 log(i/i_o) = amount of energy hitting a certain area in a certain time.
