Lesson 6: Acoustics Key Terms
Amplitude
The intensity of the energy of a vibrating body.
Absorption
The opposite of reflection. Sound is dampened by soft surfaces in an environment and reverberations and echoes are reduced.
dB HL reference
Audiometric zero
db SPL reference
0.0002 dyne/cm2 or 20μPa
Phase
Describes the position in the cycle of one sound wave relative to another
Rarefaction
When air molecules are less dense and spread further apart than normal.
Frequency
Number of complete compression-rarefaction cycles per second
Compression
When air molecules are pushed together, making the molecular density greater than when at rest.
Speed of sound
767 miles per hour or 242 meters per second.
Pure tone
Produced by simple repeated alternations of compression and rarafaction.
Boyle’s Law
States that as the physical volume that contains a gas decreases, the pressure of the gas increases.
Acoustics
Branch of physics specializing in sound.
Wavelength
The distance between one wave crest or trough and the next.
Sound pressure
The deviation from the ambient atmospheric pressure caused by a sound wave.
dB HL
Decibels Hearing Level: represents the average softest intensity level that individuals with normal hearing can detect. Audiograms are written in dB HL.
Complex wave
Acoustic combination of several different pure tones presented simultaneously.
Reflection
Sound that is reflected or bounced around by hard surfaces in the environment. Two types are reverberations and echoes.
dB SPL
Decibels Sound Pressure Level: The objective strength of a sound’s output not related to any individual’s hearing.
Resonance
The natural tendency for an object to vibrate with greater amplitude at one frequency than at others when a driving force is applied.
dB SL reference
The patient’s threshold
dB SL
Decibels Sensation Level: Sensation level above the patient’s threshold. If threshold at 1000 Hz is 20 dB HL and a tone is presented at 40 dB HL, that person is getting a presentation of 20 dB SL.
Period
The time required for one complete cycle of compression and rarafaction.
Decibel (dB)
Logarithmic scale used to denote the intensity of a sound.