Acoustics and Interior Design
Architectural acoustics is both an art and science. Acoustic features in interior spaces is as important as in a public space. Acoustic values must be considered both at the construction stage as well as at interior design/decoration stage. Surprisingly but naturally most of us realise this only after occupancy. This makes the job of interior designers more important as well as more complicated and challenging.
Any interior should sound as good as it looks. It should be pleasing the eyes as well as pleasant for the ears too as we work or live there. Architectural acoustics plays a vital role in achieving this and provide satisfying experience.
Points to consider while designing acoustically acceptable spaces:
- Sound requirements for the space.
- Who uses the space, how and for what purpose.
- Interactions, privacy and ambiance needed.
- Sources of sound both inside and outside the space.
- Effect of surface materials, fixtures and furnishings.
- Assess design options for acoustics enhancement.
- Convenience and wellbeing of people living/working in that space.
- Type of acoustic panels that serve the purpose best.
And of course, the constraints of budget and other limitations.
Importance of Acoustics
Acoustics is inherently linked with aural (sound) communication.
Large specialized rooms like auditoriums, gyms, and cafeterias needs careful acoustical engineering and should be designed using certain thumb rules:
The importance of acoustics is not limited to rooms. Noise in corridors and public spaces can also be too reverberant and soar the voices louder and louder. This background echo must be overcome. Sound is an important navigational tool. and either end of the reverberation
Sound is created by vibrations of air or other materials. When we speak, our vocal cords vibrate and creates vibrations in the air that travel to the ears of the listeners like ripples in a pond when you throw in a stone. When the sound is higher, the waves are closer together (higher frequency) and when the sound is lower, the waves are farther apart. Longer waves (lower sound) pass through thinner materials and curve more easily around barriers. Shorter waves (higher sound) are reflected by relatively thin materials and don’t bend much around barriers. Nearly all spoken sound is in the range of 125 Hz (cycles per second) to 4,000 Hz, although people can hear from about 20 Hz to 20,000 Hz. All sound waves carry well through open air, or even small holes and cracks in walls and ceilings. Even a small hole will let through a lot of sound because of the logarithmic nature of sound.
Why Acoustic Panels:
Unwanted sound is Noise and it can be a nuisance. It can disturb and distract us; harm us physiologically and psychologically. In a large room with several groups of people in conversation, the overall effect is a lot of noise. Enough sound must be absorbed instead of reflecting off the walls. Typical cafeterias are built without much sound absorbing material, so they are very noisy.
Acoustic panels help reduce the noise from activity in the room. Sound waves produced by conversation, music, phones or other sounds reverberate too long as a result of hard surfaces such as concrete, glass, drywall, and even wood. Acoustic Panels absorb the reflected energy which causes “echo” within a space and speech becomes clear; Listening becomes easier and music sounds better; People tend to become more efficient, effective and relaxed. Learning is about concentration, and external noise is a major distracting factor in education.
To reduce sound energy entering from outside through doors, walls or windows you need specific building products and construction techniques to block sound transmission between spaces.
Interior acoustics is about the airborne sound inside the room, how it interacts and proliferates with the room’s surfaces and objects.
Sound propagates at 344 m/s (1,250 km/h) at room temperature and results in multiple reflections with walls or objects before a sound wave subsides below the audible threshold. There can be three outcomes with the incoming sound energy depending on the type of object it interacts:
- Absorption:A porous material absorbs sound and the sound wave propagate into them.
- Scattering:The sound waves may reflect randomly in an unordered way as per the object they interact.
- Reflection: A hard surface such as concrete, glass or wood, acts as a mirror for the sound wave and thus reflects it.
All three processes are important and must be carefully considered while creating the acoustics of a room. Desired acoustic levels inside the room can be achieved by affecting the reflection of sound waves walls or objects.
Acoustic characteristics of a completely flat glass surface is dominated by pure reflection as it has very little absorption and scattering. An upholstered sofa, due to its softness and shape on the other hand, is dominated by absorption and scattering.
Good room acoustics are seldom noticeable but experienced. The acoustic properties of a room have a lot to do with the activity in the room. There is nothing like universally good ready made room acoustics because there can be so many different activities that can take place in the same room. Each activity has its own challenges and consequences on its acoustic design.
REVERBERATION TIME IS THE MOST COMMON MEASURE IN INTERIOR ACOUSTICS.
The reverberation time is the time that a sound takes to subside from its original sound level. It is a measure of a room’s echo. The absorption area is the area of “perfect” sound absorbers inside the room and is commonly measured in m2S (square meters Sabine).
Additionally, there are many other acoustic measures that can be used when designing room acoustics, e g STI (Speech Transmission Index), C50 or C80 (Clarity) and G (Room strength).
Absorption and Reflection of Sound
Sound waves can be reflected or absorbed. The science of acoustics is all about what to reflect and what to absorb. It is a fusion and striking a balance between reverberation, reflection and absorption. Music needs higher levels of reverberation than speech. Moderate amounts of reflection are useful to reinforce the sound as long as the overall decay time is not too long. An acceptable reverberation time for classrooms is about .75 seconds for interactive spaces and 1.0 seconds for lecture halls where as a two second reverb time for a symphony hall.
Absorption of sound is particularly difficult in special environments like cafeterias, kitchens, gymnasiums, and swimming pools. Conventional materials may be subject to damage, absorb odours, or be incompatible. However, other compatible materials do exist.
Transmission of Sound Between Rooms
One of the major challenges in acoustics is the control of noise from one room to another. The STC rating (Sound Transmission Class) of a wall is reflected by the range of speech blocking factor. As with absorption, different materials transmit more or less sound at different frequencies. Unlike the NRC (Noise Reduction Coefficient), the STC takes into account the performance of the wall at its worst frequency. The STC value of a wall is a relative indicator of diminution that can be expected from a wall system.
If the background noise is higher than the amount of sound passing through and around the wall, then the sound won’t be hear from the adjacent room. The background noise in the receiving room is critical to sound transmission. If background noise is lower than what’s transmitted, then sounds from the adjoining space would not be heard. That means some acoustical problems can be overcome by increasing background sound, but that can also pose problems as people have to raise their voices to be heard.
Most media like videos, CD/DVD, Internet content etc., now include sound and sound amplification plays a major role. A room needs be friendly and provide for a loudspeaker system. These systems can be built in or may be portable.
Some Myths and Truths
- Myth: Noise can be controlled just by installing carpet.
- Truth : Carpet is not the sole remedy for all acoustical issues. It can be effective for reducing noise from movement of furniture and foot falls. However, the carpet system absorbs mostly the high frequencies of speech only.
- Myth: Ceiling tile is enough.
- Truth: Acoustical ceiling tile, can be a very effective means of absorbing sound. There are many types of tiles with different absorption characteristics (wood fibre, mineral fibre, glass fibre, etc.) To ensure effectiveness, one has to match the acoustical problem to the solution. Misplaced or poorly selected acoustical material can result in louder voices and defeat the purpose.
In acoustics, the energy of sound waves is being taken in and trapped within the material rather than being bounced off or reflected. Materials are rated in terms of their ability to absorb sounds.
Gyptech Systems Pvt. Ltd. manufactures and supplies a wide variety of reliable acoustical products for ceilings, walls and paneling. Visit our website for further details.
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