13520328
Description
Mind Map by Luke Byrne, updated more than 1 year ago
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Created by Luke Byrne
about 6 years ago
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Acoustics
- Speech Chain
- Ling > Phys > Acoustic > Phys > Ling
- Ling > Phys > Acoustic > Phys > Ling
- Propagation of sound
- Sine wave
- Particle move & pressure variation in space
- Pure tone
- Basis of complex, periodic sounds
- Basis of complex, periodic sounds
- Particle move & pressure variation in space
- Sine wave
- Sound waves
- Frequency
- Hz (number of cycles per second)
- Healthy ear: 20-20,000Hz
- Cycle (complete vibration)
- Period = T = duration of complete cycle (s)
- T = 1/f (s)
- T = 1/f (s)
- Period = T = duration of complete cycle (s)
- Healthy ear: 20-20,000Hz
- Speed of sound
- c = 331.4*sqrt(1+Temp/273)
- c = 340 m/s as approx value
- c = 340 m/s as approx value
- Freq. does not determine speed a wave travels at
- c = 331.4*sqrt(1+Temp/273)
- Wavelength (spatial period of wave)
- λ = c / f [m]
- λ = c / f [m]
- Pitch
- Freq. closely related to (but not the same as) pitch
- Freq = physical props. of sound
- Pitch = sensation
- near-linear up to 1 kHz - listener's sensitivity decreases as we go higher in freq.
- Freq = physical props. of sound
- Freq. closely related to (but not the same as) pitch
- is independent of
- Tuning fork emits the same
freq. regardless of how
hard it has been struck
- Tuning fork emits the same
freq. regardless of how
hard it has been struck
- Hz (number of cycles per second)
- Amplitude
- dB (size of variation in air pressure)
- peak deviation from normal atmospheric pressure
- how forceful the wave is
- Decibels = relative loudness of sounds in air
- Decibels = relative loudness of sounds in air
- peak deviation from normal atmospheric pressure
- dB (size of variation in air pressure)
- Phase
- degrees (starting point of
a wave along the y-axis)
- Situation of the cycle of oscillation at a particular moment
- Two Sine Waves added
- In-phase = largest output
- In intermediate phase = intermediate output
- In opposite phase = zero output (silence)
- In-phase = largest output
- degrees (starting point of
a wave along the y-axis)
- Frequency
- Sound Classification
- Periodic
- Complex
- >1 frequency
- freq's which are int. multiples of
lowest one = fundamental = f0 = H1
- Power Spectrum (Amp Spectrum or Magnitude Spectrum)
- >1 frequency
- Fourier's theorem
- A periodic function, f(x), which is
reasonably continuous may be
expressed as the sum of a series
of sine or cosine terms (called
the Fourier series), each of
which has specific AMPLITUDE
and PHASE coefficients (known
as Fourier coefficients)
- Fourier Transform
- Discrete Fourier Transform (DFT)
- Time-domain to Freq-domain
- Freq-domain repres. = Hz (freq - X) vs. dB (amp - Y)
- Freq-domain repres. = Hz (freq - X) vs. dB (amp - Y)
- Time-domain to Freq-domain
- Fast Fourier Transform (FFT) - fast algo for DFT
- Breaks into sine and cosine waveforms
- Discrete Fourier Transform (DFT)
- Fourier Transform
- A periodic function, f(x), which is
reasonably continuous may be
expressed as the sum of a series
of sine or cosine terms (called
the Fourier series), each of
which has specific AMPLITUDE
and PHASE coefficients (known
as Fourier coefficients)
- Complex
- Aperiodic
- Continuous (fan, engine)
- Transient (door closing)
- Continuous (fan, engine)
- Periodic
- Sound
- Energy produced by
a vibrating source
which travels
through the air
- Vibration: simple harmonic motion (SHM)
- Elasticity (bounce back)
- Inertia (keep moving)
- Periodic
- Amp decreases
- Elasticity (bounce back)
- Vibration: simple harmonic motion (SHM)
- Movement of air particles ->
variation in air pressure
- Compression (high pressure)
- Rarefaction (low pressure)
- Longitudinal wave (pushes and pulls)
- Compression (high pressure)
- Energy produced by
a vibrating source
which travels
through the air
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