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52 Cards in this Set
- Front
- Back
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Mass
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The amount of matter present
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Elasticity
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Property that enables recovery from distortion of shapes of volume
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Newton's first low of motion
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Inertia - all bodies remain at rest or in a state of uniform motion unless another force acts in opposition.
Magnitude of inertia is directly proportional to the mass, and as a result is measure of inertia. |
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Vibratory motion
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The interaction of tow opposing forces: inertia and elasticity.
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Newton's third law of motion
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With every force there must be an equal and opposite reaction force.
For vibratory motion, elasticity is the reaction force to inertia. |
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Movement of air particles
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Density of air particles increase- compression
Density of air particles decrease- rarefaction |
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Sound is characterized by...
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propagation of density changes through an elastic medium.
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Displacement (x)
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A change in position
A vector quantity that incorporates both magnitude and direction. Contrast with scalar quantity that has only magnitude (e.g. mass) |
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Velocity (v)
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1) the amount of displacement per unit time.
or 2) the time-rate displacement Vector quantity v= displacement (x)/time (t) |
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Acceleration (a)
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The time-rate change in velocity
Vector quantity a= change in v/t Units in m/s squared |
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Force (F)
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1) A push or a pull,the product of mass (m) and acceleration (a).
2) F=ma 3) Object has mass (inertia), which opposes change in motion, force is applied to overcome inertia. 4) Consequence of force is the distortion of matter and/or the acceleration of matter. |
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Pressure (p)
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1) Force per unit area.
p=F/A Units of measure for pressure: N/m squared dyne/cm squared 1 pascal (Pa) |
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Hooke's law
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Magnitude of restoring force is directly proportional to magnitude of displacement.
F(sub r)= -kx, where k is the stiffness constant of the spring |
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Sinusoidal motion
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Simple harmonic motion can be called sinusoidal motion.
Projection of sinusoidal motion is called a sine wave or sinusoidal wave. |
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Two characteristics of sound wave propagation
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1) Rate (frequency) of vibratory motion
2) Rate (speed) of wave propagation |
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Speed of sound
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331 m/s at sea level and temp 0 degrees C
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Sound intensity is measured in...
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watts/meter squared
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Sound pressure is measured in...
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micropascals
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Does 0 dB IL mean the absence of sound?
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No it only means that the measured sound intensity is the same as the standard reference intensity.
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Simple periodic vibration
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The vibratory pattern repeats at regular intervals. Sinusoidal. Ex. pure tone
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Complex periodic vibrations
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Any sound wave that is not sinusoidal. Two or more pure tones are combined into a nonsinusoidal pattern that repeats itself as a function of time. A series of simple sinusoids that can differ in amplitude, frequency, and phase. Called a Fourier series. A Fourier series can be derived by a process called Fourier analysis.
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Aperiodic vibration
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The pattern of vibration does not regularly repeat itself over time. No periodicity. Ex. noise, speech sounds like "s," "sh," "f," "th"
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Continuous spectrum
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Shows that there are infinite frequencies present over the indicated range.
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Line spectrum
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Vertical lines at discrete frequencies. As seen for periodic vibrations.
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White noise
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An infinite number of frequencies with random phases and equal amplitude over the entire frequency range.
An aperiodic waveform with equal energy in every frequency band 1 Hz wide. Spectral envelope slope of 0 dB/octave. |
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Fundamental frequency
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The lowest frequency component in a complex periodic vibration.
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Cut-off frequency
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The point which is 3 dB less than the peak.
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What determines the natural or resonance frequency of a elastic system?
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Mass and stiffness
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The two components of impedance (Z)
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Energy dissipating - Resistance (R)
Energy storage - Reactance (X) |
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Quality factor (Q-factor)
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The sharpness of a peak for a frequency response output. Ratio of the height to its width.
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Standing waves
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Occurs when two progressive waves, incident and reflected, of the same frequency and amplitude travel in opposite directions in or along some medium.
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Refraction
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Bending of sound waves due to a change in speed of propagation.
When a wave encounters an obstacle offering a large impedance, the wave is reflected with no change in speed of propagation. |
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Diffraction
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When a wave bends around an object.
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Absorption
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Opposition to sound transmission will exist at any boundary where the impedance differ. If impedance is infinite, intensity of reflected wave will equal intensity of incident wave. If impedance is not infinite, some sound energy will be absorbed by the new medium.
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The Doppler Effect
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If a source moves toward an observer, then pitch rises.
If a source moves away from an observer, then pitch falls. |
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Loudspeakers
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Radiate sound into an unconfined space. The source is a vibrating diaphragm that is usually a shallow, stiff cone made of lightweight paper. Vibrations are damped from the interaction with the air and the creation of sound waves.
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Audiometric earphones
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Coupled to ear to provided a uniform frequency response and for very low distortion over a wide range of frequencies and output levels.
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Audiometric Bone Oscillator
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Held against the mastoid to provide direct bone-conducted stimulation of the cochlea.
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Square wave
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1) A complex periodic wave
2) Sine waves with identical starting phases. Each component is an odd integer multiple of the fundamental frequency. 3) Spectral envelope slope of -6 dB/octave. |
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Sawtooth wave
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1) A complex periodic wave
2) Sine waves with identical starting phases. The components are odd and even integer multiples of the fundamental frequency. 3) Spectral envelope slope of -6 dB/octave |
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Amplitude spectrum
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A graphic alternative to the waveform.
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Phase spectrum
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Identifies the starting phase as a function of frequency.
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Sampling
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Measure from a complex wave as a series of samples taken at regular intervals. Provides incomplete information so careful interpretation required.
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Aliasing
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If the sampling rate is too low compared with the frequency being sampled, then a low frequency signal is determined when the signal is actually a higher frequency. Can be eliminated by sampling at a rate at least twice that highest frequency (2f) within the complex tone.
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Fourier analysis
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Any complex wave can be decomposed to determine the amplitude, frequencies, and phases of the sinusoidal components.
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Signal Averaging
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Evoked potentials are directly related to the stimulus such that the potentials repeat themselves after the stimulus presentation.
Noise is predominantly random, aperiodic, and generated from many different sources. Sources of noise include: Internal- respiratory, circulatory External- electrical interference Acoustic energy of the noise is proportional to 1/N (N=number of samples or sweeps you record) Signal repeats itself constantly so it does not depend on the number of samples. Signal averaging is the measurement of a constant signal (evoked potential) and the average noise component that decreases with increasing sample size. |
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Types of distortion
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1) Frequency
2) Amplitude 3) Transient |
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Frequency distortion
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Frequency selective system, filtering occurs and system undergoes frequency distortion.
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Linear systems
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As input amplitude increases, output amplitude increases proportionally. Output may not equal input, amplification or attenuation may occur.
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Transient distortion
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Amplitude rises over time from zero to a maximum, the amplitude may or may not plateau, and then falls over time from a maximum to zero.
Rise-plateau-fall time or rise-fall time. |
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Amplitude distortion
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The input signal exceeds the limits of linearity and the result is peak clipping.
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Intermodulation distortion
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When a driving signal is complex, the system will experience nonlinear distortion. Frequency components of the output signal include harmonics and combination tones.
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