10 Questions
What is the unit of measurement for sound intensity?
Watts per square meter
How is Sound Pressure Level (SPL) defined?
The measurement of sound intensity between actual sound pressure and a reference pressure
Which term refers to the local pressure deviation from the ambient atmospheric pressure caused by sound waves?
Sound Pressure
What is the SI unit for sound pressure?
Pascal (Pa)
What helps distinguish between a note of high frequency and low frequency?
Pitch
What is the measurement unit for SPL?
Decibels (dB)
What does Sound Level represent?
Measurement of sound intensity in watts per square meter
What does the term 'Disordered' refer to in the context of sound?
Presence of all pitch frequencies but irregular in nature
In architectural acoustics, what is the problem related to sound transmission between rooms?
Behavior when rooms are separated by a common wall
What does Pitch help distinguish between?
Note of high frequency and low frequency
Study Notes
Sound Waves and Properties
- Sound waves are graphical representations of complete to and fro oscillations of vibrating particles in a sound field.
Structure-Borne Sound
- Medium: concrete, steel, wood, glass, and combinations
- Vibrating particles in a sound field
Acoustic Enclosure
- A structure built around a machine to reduce noise
Sound Magnitude
- Refers to loudness, which is subjective and ear-oriented
- Measured in sound pressure level (SPL), sound intensity, and sound intensity level (SIL)
Sound Levels
- Intensity level is the ratio between a given intensity and a base intensity
- Measured in decibels (dB)
- Direct sound: reaches a given location through a straight line from the source
- Intensity level is a dimensionless quantity telling the level of sound relative to a fixed standard
Sound Power
- Total sound energy radiated by a sound source
- Measured in watts (W)
- Product of sound pressure and volume velocity
- Also labelled as Acoustical Power
Sound Transmission
- Transfer of sound energy through a barrier from one medium to another
- Transmission loss properties of a partition are rated on the Sound Transmission Class (STC)
Ambient Noise
- Total noise level in a specified environment
Attenuation
- Reduction of noise or vibration
- Expressed in decibels (dB)
Airborne Sound
- Sound or noise radiated directly from a source into the surrounding air
Near Field and Far Field
- Near field: area surrounding the noise source, sound does not decay at 6dB for a doubling of distance from the source
- Far field: part of the sound field where the sound wave spreads spherically, sound decays at 6dB for a doubling of distance from the source
Sound Insulation and Absorption
- Reduction or attenuation of sound by a solid partition between source and receiver
- Includes building walls, floors, barriers, and acoustic enclosures
- Averages room absorption in Sabins or Metric Sabins, divided by total room surface area
Sound Velocity and Wavelength
- Sound velocity depends on the medium and temperature
- Wavelength is a measure of distance between two identical peaks or crests in a wave
- Velocity is usually expressed in feet per second
Frequency and Period
- Frequency is the speed of vibration, determining pitch
- Measured as the number of wave cycles in a second
- Period is the time taken for one complete cycle of vibration to pass a given point
- Frequency increases, period decreases
Amplitude and Loudness
- Amplitude is the fluctuation or displacement of a wave from its mean value
- Experienced as loudness, which depends on intensity and sensitiveness of the ear
- Timbre is the quality of sound, enabling distinction between two sounds of the same loudness and pitch
Test your knowledge on structure-borne sound and sound magnitude with this quiz. Learn about the characteristics of oscillation of vibrating particles in a soundfield, wave motion, layer of refraction, compression, acoustic enclosures, and more.
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