Architectural Acoustics Quiz

Architectural acoustics is the science and engineering of achieving good sound within a building.
It's a branch of acoustical engineering.
It's about achieving good speech intelligibility in spaces like theaters, restaurants, or railway stations.
It's also about enhancing music quality in concert halls or recording studios.
It's about suppressing noise to create productive and pleasant work and living spaces.
Architectural acoustic designs are typically done by acoustic consultants.
Symphony Hall, Birmingham is an example of architectural acoustics application.

Reverberation is the persistence of sound after the sound source has stopped.
It results from repeated reflections.
Reverberation time is the time it takes for sound to decay to an inaudible level.
Reverberation time is measured in the time needed for sound energy to decay by 60 decibels.
The reverberation time of a space is determined by the use of the space.
Appropriate reverberation times for speech in smaller rooms are between 0.3 and 0.6 seconds.
Auditoriums need reverberation times between 1.5 and 1.8 seconds.
The amount of absorptive or reflective finishes in a space affects the reverberation time.

It's the decrease in the intensity of sound energy as it spreads over a wide area.
Attenuation depends on the distance from the source.
Processes like scattering, absorption, or spreading in three dimensions affect attenuation.

Natural sound reinforcement happens when sound reflects from various surfaces.
Covering ceilings of meeting rooms and auditoriums with sound-absorbing materials can reduce reverberation.
It's preferred to leave some parts of a room as reflecting surfaces to avoid need for electronic reinforcement systems.

Echoes are a result of multiple reflections that produce confusing sound.
Multiple reflections causing echoes result from sound waves reflected from a surface loud enough to be noticeable and received late enough to be perceived distinctly from the source.

Focusing happens when sound waves converge at a singular point when reflected from a concave surface.
The sound is very loud in the focal point of a concave surface, but it's markedly reduced elsewhere.
A "whispering gallery" is a room with concave surfaces that can enable people to hear each other's whispers across the space clearly while unheard across the rest of the space.

The human ear is sensitive over a wide range of sound power (measured in watts).
Decibels (dB) is a logarithmic unit of measure for sound intensity.
The subjective experience of loudness varies greatly from actual sound power.
Doubling the actual sound intensity is perceived only as a barely noticeable increase in perceived loudness.
The threshold of pain, which means the level above which sounds are perceived as painful and damaging to the human hearing, is about 130 decibels.

Sound travels outwards in all directions from the source until encountering a surface.
Sound waves are characterized by peaks and valleys, and the distance between two peaks is the wavelength.
The rate at which the peaks pass a stationary point is the frequency (measured in Hertz, Hz).
Higher frequencies produce higher-pitched sounds.
Lower frequencies produce lower-pitched sounds.
Wavelengths of sounds vary greatly.

The history of modern acoustics started with the design of the Fogg Art Museum Lecture Hall at Harvard University.
The architect Wallace Clement Sabine solved the acoustic problem of the lecture hall by developing equations and coefficients for reverberation and absorption of many materials.

Materials like brick and concrete have a high mass, therefore attenuating sound effectively.
Normal-weight concrete is an effective material for sound attenuation in building constructions.
Lightweight concrete is less effective than normal-weight concrete for sound attenuation.
Aerated concrete is more porous, therefore, more effective for absorbing sound.

Smooth, solid materials like plaster and painted concrete have low levels of sound absorption.
They reflect most sounds and are used as effective sound reflectors in constructions.
Glass resists sound attenuation but is highly effective for sound reflection.

Absorptive materials lessen reverberation by absorbing sound, therefore they change the room's characteristics from having many sound reflections to having substantially fewer.
The absorptive qualities of materials affect the room's noise-reduction capabilities, especially in spaces with concentrated noise sources and distributed sound sources.
Materials are neither perfect reflectors nor absorbers of sound, hence the coefficient of absorption measures how efficiently materials absorb sound or reflect sound.

Installation method affects the absorptive capability of materials for sound attenuation.
Methods include rigidly fastening, nailing to furring strips, suspending from ceilings or walls.
The optimal method affects the degree of sound absorptive capability, notably for high-frequency waves that may not reach the ceiling until after the third reflection off a surface.

Impact noise results from physical impacts on surfaces, such as footsteps or furniture.
The impact insulation class (IIC) rating measures the quality of a building structure for preventing the transmission of impact noise.
High IIC ratings reduce the level of impact noise that can transmit between spaces, therefore, lower ratings are associated with less isolation for sound attenuation.

Sound level in one space is influenced by its absorption, its transmission loss, and its wall surface area.
The background sound level can affect whether sound in another space is heard or masked.

A near field is the region about a sound source where sound intensity is relatively higher and varies with distance from the source.
A reverberant field is the region where reflection is uniform throughout the space

Acoustical ceiling tiles are available in various sizes and textures using absorbent materials like cork and fiber.

Proper design considerations focus on mitigating and controlling sound reflections in spaces that need sound control to maintain proper levels of audibility.
Acoustic design of spaces involves planning and shaping the space to manage sound efficiently, such as for speech intelligibility or music appreciation.

Regulations from local governments are used for setting standards and limits on noise, and on the amount of sound produced by diverse sources; these vary by industry.
Occupational Safety and Health Administration (OSHA) regulations require hearing protection for workers exposed to high noise levels, hence, to maintain employee safety.
Exposure to excessive noise can result in both temporary and permanent hearing impairments, and other ailments like headaches and digestive or cardiovascular problems.

Reducing noise can be done by using mechanical and utility areas as sound buffers; locating quieter rooms as far from noise sources as possible; using heavyweight, airtight construction; using window and openings to control the path that sound will travel.
Multiple glazing for windows and installing duct linings are typical ways to reduce noise.