Hearing and Sound Flashcards
Parts of the Ear (5)
Outer Ear Ear Canal Ear Drum Middle Ear Cochlea
Ear processing sound waves
Converts sounds from waves to mechanical movements then to electrical signals
Vibration and sound process (3)
- way to produce sound
- compression pushed molecules together
- rarefaction pulls apart
Anatomy of a wave (3)
Frequency
Wavelength
Amplitude
Frequency Definition
Number of times a complete cycle occurs per second
Wavelength Definition
Physical distance between two points exactly one cycle apart
Wave Anatomy Inversely proportional
frequency and wavelength. as one get larger the other gets smaller
Maximum Compression location in a waveform
at top of waveform
Rarefraction location in a waveform
parts below the reference level
Maximum Rarefraction location in a waveform
bottom of waveform
Amplitude Def
Magnitude of a signal, intensity of wave
Pitch Def
Wavelength (Frequency) determines pitch
Frequency Range we can hear
20 Hz to 20,000 Hz
Octave def
Interval of tones between a frequency and doubling of that frequency
Logarithmic in relation to hearing (2)
The human’s ear’s response to frequency is logarithmic
The way we hear is exponential
Bands def (2)
Frequencies can be divided into bands.
Spectrum of hearing is divided into 10 bands where each represents an octave
Harmonics def (3)
- sounds are complex waveforms that can be broken down into individual sine waves
- complex waveforms is made up is made up of fundamental frequency plus whole number multiples of that frequency
- whole number multiples are harmonics
Complex waveforms def
comprised of a fundamental frequency plus many harmonics
Logarithms def
Number of time the number 10 must be multiplied by itself to get a certain value
Logarithmic Scale def
Scale with each unit representing a ratio of 10:1
Human Perception of Sound (2)
Humans perceive differences in sound levels logarithmically not linearly.
The 10 logarithmic scale is used to measure, record and discuss sound level differences
Felhner-Weber Law
The intensity of a sensation is proportional to the logarithm of the intensity of the stimulus
Decibels def
Unit of Measurement to describe base 10 or 20 logarithmic relationship of a power ration between two numbers
Decibel Equations
We can state the difference in decibels for two powers, voltages or distances
Decibel Formula for Power
dB = 10 * log(P1/Pr)
Decibel Formula for Voltage
dB = 20 * log(V1/Vr)
Decibel Formula for Distance
dB = 20 * log(D1/Dr)
Smallest Perceptible change in human hearing
1 dB
Just Noticeable Change
3 dB
Double the perception of hearing
10 dB
Inverse Square Law and Light, Gravity and Electric Field
Every time the distance doubles from the source of energy the energy spreads out and covers 4 times the area. Subsequntly, the energy is 1/4 of what it was previously. *Does not apply to sound: light, gravity and electric field
6 dB Per Doubling Rule
Sound pressure is reduced by 6 dB every time the distance is doubled
