Basic Elements Of Acoustics Flashcards
What is sound?
Repetitive changes in air pressure that propagates in waves
What happens to particles that carry the sound wave?
The particles oscillate back and forth but do not propagate with the wave signal (e.g., think of a wave in a stadium). Particles remain around a fixed point.
What are the 3 characteristics of sound?
Amplitude (loudness)
Wavelength
Frequency (pitch)
What is amplitude measured in?
dB (decibels)
What is the human hearing threshold?
0 dB
What is wavelength?
Distance between peaks
What does frequency measure?
Cycles per second (Hz)
What range of frequencies are humans sensitive to?
20-20,000 Hz
What does a higher frequency indicate?
Higher pitch
What does a larger amplitude indicate?
Louder sound
What does a short wavelength refer to?
High frequency
What does large wavelength refer to?
Low pitch sounds
What is measured in dB?
Sound pressure (amplitude)
Are most sounds pure sine waves?
No. Most sounds are complex sounds.
Who is Fourier?
Mathematician
What did Fourier say about waveforms?
Every periodic waveform is composed of harmonically related sinusoids with unique amplitudes
What is the fundamental frequency?
The musical pitch of a note that is perceived as the lowest
The lowest frequency sinusoidal in the sum
What are abbreviations of the fundamental frequency?
fo
FF
How do our ears identify the fundamental frequency?
Our ears identify the FF as the specific pitch of the musical tone (the individual frequencies are blended together by our ear/brain into a single tone)
The FF is the loudest frequency
What are most natural sounds made up of?
One fundamental frequency
Several harmonics of the fundamental frequency - waves of the frequency that is a positive integer multiple of the fundamental frequency
Additional frequencies
What does Fourier analysis of a waveform show us?
Can see the distribution of the frequencies from which the waveform is made of
Can see the decomposition of the wave
What is a sound a mix of?
A mix of fundamental and different additional frequencies
Describe the amplitude of additional frequencies
Lower amplitudes than the FF, thus they are not as loud
Will violin and piano produce same or different waveforms?
Different waveforms
What can the FF be decomposed into?
Several simple sine waves
Will violin and piano have the same or different FF?
Same FF (220 Hz)
What is timbre related to?
Related to the harmonic structure of a tone
Why might tones of the same loudness, pitch, and duration sound different?
Different timbre
What is the Power Spectrum of a signal?
The representation of sounds by the intensities (dB) of their simple sound waves
The presentation of the distribution of frequencies
