Acoustics 1 Flashcards
What is the definition of frequency
The number of oscillations in a given unit of time (e.g. 1 second), measured in Hertz (Hz)
What is the definition of Fundamental Frequency?
The lowest frequency of a periodic waveform
What is the definition of a periodic sound?
A sound wave that has regular or repeating patterns of compression and rarefaction due to the oscillation of the mechanical sound source
What is the definition of an aperiodic sound?
A sound wave produced by mechanical sources that have no regular oscillating movement, and thus having no pitch
What is a complex sound wave?
Sound waves that have more than 1 frequency (can be periodic or aperiodic) → can be viewed as a combination of simple sine waves → can be periodic or aperiodic
What is a simple sound wave?
Periodic waveforms that consist of only 1 frequency (aka sine waves/ pure tones) → never naturally occuring
What is the definition of wavelength?
The distance travelled by one cycle of the waveform
What is the definition of phase?
Relative timing or position of a sound wave at a given point in time → usually the starting tone of a waveform with respect to the next tone
What is the definition of amplitude?
The amount of change in air pressure produced by a sound source (aka the amount of displacement of air particles from their point of equilibrium)
What is Pascals?
The unit of measurement for air pressure that denotes force per unit area
What is dB SPL?
a relative measure of sound pressure level with respect to a reference (e.g. human hearing range)
What is dB IL?
a relative measure of sound intensity level with respect to a reference (e.g. human hearing range)
What is spectral analysis?
An analysis that decomposes any sound wave into its simple sinusoidal components
What are harmonics?
A harmonic is a wave or signal whose frequency is an integral (whole number) multiple of the frequency of the same reference signal or wave
What is pitch?
The psychological correlate of the fundamental frequency of a periodic sound wave
What is loudness?
The psychological correlate of amplitude
What is sone?
A unit used to measure the psychological scale for loudness
What is mels?
A unit used to measure the psychological scale for pitch
What is the range of sound intensities humans can usually hear?
0 dB to 120 dB
Identify common dB levels of sounds.
Whisper (30dB), screaming (90dB/ threshold for endangering hearing), concert (120dB/ threshold for pain), and jet engine (150dB/ total deafness may occur)
Identify the range of sound frequencies humans can normally hear.
20 Hz to 20,000 Hz
Identify the range of frequencies associated with human speech.
85 to 155 Hz for males and 165 to 255 Hz for females
Compare the physical scales for sound intensity and frequency with their respective psychological dimensions.
Sound intensity is known as amplitude (dB) and is the physical correlate of loudness (sone). Frequency (Hz) is the physical correlate of pitch (mels).
Label the axes of a time amplitude waveform and a spectrum - including units.
For a time-amplitude waveform, the x-axis is amplitude (dB) and the y-axis is time (s). For a spectrum the x-axis is frequency (Hz) and the y-axis is amplitude (dB).
Why are harmonic peaks evenly spaced from left to right across the frequency dimension?
Harmonics are integral multiples of the fundamental frequency of a soundwave, thus their peaks are evenly distributed.
