Sound Control in Building Construction – Glossary

The following is a brief collection of terms related to the design of sound control in buildings.

The primary concerns in sound control for building designers are:

1. Room Acoustics – Controlling the experience of sounds within an enclosed space.
2. Sound Privacy – Keeping sound enclosed within a given area.
3. Noise Control – Preventing undesired sound.

A-Scale

Reference intended to match the response characteristics of the average human listener. called dBA.

Absorbers

Materials that have the capacity to absorb sound, such as acoustical tile and panels, carpeting, draperies, and upholstered furniture.

Absorption

Taking up and holding or dissipating of matter or energy as a sponge takes up water. Absorption is the opposite of reflection.

Acoustical Privacy

State of sufficient insulation (protection) from intruding and disturbing noise.

Acuity

Relative clarity (sharpness, keenness) of sound communication.

Ambient

Existing surrounding conditions. Ambient noise level refers to the existing conditions in a space as a result of enduring sounds from all sources.

Amplitude

Measurement of sound level in wavelength terms.

Attenuation of Sound

Reduction of sound energy as it passes through a conductor, resulting from the conductor’s resistance to the transmission.

Barrier (Sound)

Structure that impedes direct sound transmission

Complex Waves

Sound waves combining two or more frequencies

Concave

Curved toward the observer. Cupped.

Conductor

Material that carries or transmits energy from one location to another. A conductor of sound must be an elastic material.

Convex

Curved away from the observer. Rounded.

Criteria

Standards by which performance can be judged.

Crosstalk

Two-way exchange of sounds between spaces through a connecting sound path. Usually a flanking or leaking path (connecting ducts, pipe chases, back-to-back wall fixtures, etc.).

Cycle

One complete phase of an action, such as one revolution of a wheel or one full swing of a pendulum.

In relation to sound, one to-and-from movement of the vibrating object or one high-low pressure sequence of a sound wave.

Damping

Effect that reduces the amplitude of a vibration

Decibel (dB)

Unit adopted for the convenience in representing vastly different sound pressure.

It is 20 times the logarithm to the base 10 of the ratio of the sound pressure to a reference pressure of 0.0002 dyne/cm^2.

This reference pressure is considered the lowest value that the ear can detect.

Density

Ratio of the mass (or weight) of a body to its volume. A common unit of measure is pounds per cubic foot.

Diaphram

Thin body that separates two areas. In sound, the skin of a partition or ceiling that separates the room from the structural space in the center of the partition of ceiling assempbly.

Diffraction

Change in direction that occurs when a wave contacts a space, surface, or edge smaller than the wavelength.

Diffuse

To spread out evenly and thus become less dense or concentrated.

Displacement

Forced movement away from an original location.

Dominant Pitch

Subjective response of the ear to the fundamental frequency of a sound. Usually louder tahn the harmonic overtones and of lower frequency.

Dyne

Unit of force. Specifically, the force required to accelerate one gram of mass one centimeter per second.

Elastic

Capacity to return to original shape after deflection.

Energy

Ability to perform work. In sound, the capacity to compress the conductor of molecules.

Flanking

Taking a path around something, such as a sound barrier.

Flanking Transmission

Transmission of sounds by indirect paths; around, rather than through, intervening barriers.

Frequency

Number of times than an action occurs in a given time period.

In sound, the number of complete vibration cycles per second represented by the unit hertz (Hz).

Fundamental Frequency

Dominant and usually lowest frequency of a sound which establishes the frequencies of the harmonics.

Harmonics

Secondary frequencies that are whole-number multiples of the fundamental frequency of a sound.

The harmonics combine with the fundamental frequency to produce the complex sound wave, giving timbre or quality to the total sound as perceived.

Hertz (Hz)

Unit of measure of frequency, representing cycles per second.

Homogeneous

Of uniform composition and structure.

Impact Insulation Class (IIC)

Whole, positive number rating, based on standardized test performance, for evaluating the effectiveness of assembles in isolating impact sound transmission.

Intensity

Rate of sound energy passing through a unit of area.

Masking (Sound)

Added sound that increases the background noise level to reduce perception of incoming noises.

Mitigation

Reduction of the effect of something (general definition).

Murphy’s Law

Anything that can go wrong will go wrong.

Noise

Undesired sound; usually of a disturbing nature or causing interference with some hearing task.

Noise Reduction Coefficient (NRC)

Mathematical average of sound absorption coefficients recorded at the frequencies of 250, 500, 1000, and 2000 Hz.

Octave

Interval between a sound of one frequency and a sound with a frequency that is exactly double the first.

Octave Band

Frequency spectrum that is one octave wide.

Bands of one-third octave are used for recording sound test results and are designated by the center frequency of the band.

Overtones

Subjective response of the ear to harmonics.

Party Wall

Wall or partition separating two occupancies in a building.

Pitch

Highness or lowness of a sound as perceived by the ear.

While the frequency of the sound determines the highness, pitch is the subjective response to it.

Plenum

Enclose air space.

Pressure Waves

Layers of high and low pressure that radiate out in all directions from a sound source.

Radiate

To travel in straight lines away from a center, such as sound waves moving out from a source.

Resilient Attachment

Fastening system that reduces the transmission of vibrations.

Resonance

Sympathetic vibration of an object when subjected to a vibration of a specific frequency.

The object tends to act as a sound source.

Reverberation

Continuation of sound reflections within a space after the sound source has ceased.

Sabin

Unit of measure of sound absorption; the amount of sound absorbed by a theoretically perfect absorptive surface of 1 square foot area.

Named for Wallace C. W. Sabine, noted American physicist.

Sound

For our purposes: what is received by human listeners through the physiological process of hearing.

Sound Attenuation

See Attenuation of Sound.

Sound Conditioning

Designing and equipping a space for faithful retention of desirable sounds and maximum relief from undesirable acoustical effects.

Sound Leak

Hole or crack that permits sound to pass through a separating barrier (wall, floor, roof).

Sound Pressure

Instantaneous change in pressure resulting from vibration of the conductor in the audible frequency range.

Conversational speech at close range produces a sound pressure of about 1 dyne per square centimter.

Sound Propogation

Origination and transmission of sound energy.

Sound Transmission

Transfer of sound energy from one place to another, through air, structure, or other conductor.

Structure-Borne Sound (Noise)

Sound imparted directly to and transmitted through the building construction.

Subjective

Related to conditions of the brain and sense organs rather than to direct physical actions/

Symmetrical

State of being identical or balanced on each side of a real or imaginary dividing line.

Timbre

Subjective response of the ear to the quality or richness of a sound, produced by the number and relative energy of the harmonics and other frequencies present in the sound.

Tone

Subjective response of the ear to the pitch of a sound.

Variable

Value that changes with changes in the conditions.

Velocity

Rate of travel.

Vibration

Uniform, rapid movements of an elastic material in a back-and-forth direction.

Watt

Unit of power. Sound pressure intensity can be directly measured in watts/cm^2 or in dynes/cm^2.

Waveform

Shape of the graphic representation of a sound wave.

Wavefront

Spherical surface of the wave as it travels out in all directions from the source.

Wavelength

Physical distance between identical points on successive waves. The wavelength is a function of the frequency and the speed of sound in the conductor.