# Vocabulary to know Acoustics is the Science that deals with the waves, frequency, amplitude, pitch, transmission, reception, control, effects, and production.

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Vocabulary to know Acoustics is the Science that deals with the waves, frequency, amplitude, pitch, transmission, reception, control, effects, and production of sound. - Merriam Webster Dictionary Architectural acoustics is the science that deals with the waves, frequency, amplitude, pitch, transmission, reception, control, effects, and production of sound in buildings. Reverberation is the continuing of a sound after it’s original noise due to sound reflections.

Basic information on sound Sound is vibration in an elastic medium. A Medium is any material that can return to its original form after being deflected by an outside influence such as sound vibrations. The more elastic a material is the better conductor of sound it is. As sound vibrates through a medium it compresses surrounding particles and leaves a gap on the alternate side called a rare faction. Thus forming a sound wave.

More Info Frequency is the amount of waves produced in 1 sec. and is measured in herts. (Hz) Amplitude is how big each wave is and determines the volume of a sound. Measured in decibels (dB)

What is reverberation and the inverse square law, and what is its impact on architectural acoustics? Reverberation is the collection of all reflected sounds in a structure thus causing a continuance or extension of the original sound. Discovered and analyzed by Wallace Clement Sabine who is the Father of Architectural Acoustics. He Found out how to predict reverberation time and the unit of sound absorption was named in his honor. The Inverse square Law only applies if there is no reflection of sound or reverberation. It states that energy twice as far from its source has to cover four times the area thus reducing it’s intensity to ¼ its original and so on.

How do the materials in a building influence the factors of sound? As previously mentioned the more elastic a material is the better conductor of sound it is. For example cork and lead are very inelastic thus not a good conductor of sound. Steel is very elastic and can retain sound better. Another factor is the density of materials. Sound travels faster through particles that are close together. This is why water is a more conductive medium of sound than air. Many structures are made of steel and have huge steel beams and surfaces hidden behind walls

What other factors contribute to sound vibrations in buildings? In Architectural acoustics the design of a building depends on many things like what is the building itself going to be. (eg. Office, auditorium, gymnasium, etc…) This in turn can determine size. Different designs are desired for different purposes. In an office or restaurant you might want sound to stay controlled and direct to prevent everyone from eavesdropping in your conversation. But in a auditorium you want sound to be projected and as loud as possible, which leads to our first factor.

Sound projection A good architectural design of an auditorium would allow sound to travel all the way to the back with out dying of intensity due to the Inverse Square Law. This would include several reflective surfaces And also a high reflective ceiling to project sound to the back of the auditorium. Angles shape and size are also contributors as well.

Clarity & Balance It’s also important to keep in mind what the building is used for (e.g. recording studio, opera house, meeting hall) While reverberation increases richness and fullness of noise It also decreases clarity of voice/speech. Therefore in a music hall or The concert Hall of the Sydney opera house you want lots of reverberation and reflecting surfaces to make music sound more rich, but in a meeting hall or the Chamber of the United States House of Representatives you want less reverberation or if not you lose articulation and speech echoes and gets lost. Highly reflective surfaces lengthen reverberation time while absorbing surfaces shorten reverberation time.

Even Dispersion Angles have a big factor on sound waves in a building. It is important for sound to be evenly dispersed especially in larger areas. Often times there are spots of low intensity and high intensity in an auditorium or such and this can be displeasing. These uneven intensities are caused by angles or surfaces that cause focusing spots which focus sound to one area. In a restaurant it might be more beneficial to have reflective flat parallel walls so sound is not projected while in an auditorium angled sidewalls would be more beneficial Concave surfaces often allow focus areas which could/ could not be beneficial depending. But Convex surfaces are often refereed to as anti-focusing materials for they greatly disperse sound.

Comparing/applying real-life architecture Many of these properties are used all around us from the highly reflective high ceiling of the Kimmel Center, and the angled segments on the ceiling of the Sydney Opera house to the concave anti-focusing walls next to the stage in the auditorium of our own school. Can you point out the pros and cons of my model design of the chamber of the United States House of Representatives???

Resources 1.) USG Corporation, James D. Janning. Understanding Acoustics in Architectural Design. Retrieved from: http://www.usg.com/documents/courses/02JuneUnderstandingAcoustics.pdf http://www.usg.com/documents/courses/02JuneUnderstandingAcoustics.pdf 2.) Hyper Physics, Carl R. Nave. (2010). Architecture for Acoustics. Retrieved from: http://hyperphysics.phy-astr.gsu.edu/hbase/acoustic/arcaco.html#c1 http://hyperphysics.phy-astr.gsu.edu/hbase/acoustic/arcaco.html#c1 3.) Acoustics. (2011). In Encyclopædia Britannica. Retrieved from: http://www.britannica.com/EBchecked/topic/4044/acoustics http://www.britannica.com/EBchecked/topic/4044/acoustics 4.) Broadcast Engineering & Acoustics. Architectural Acoustics. Retrieved from http://images.jhzai.multiply.multiplycontent.com/attachment/0/SaoljwoKCpk AABtrvl01/Part%204%20-%20Architectural%20Acoustics%20- %20handout.pdf?nmid=213800995 http://images.jhzai.multiply.multiplycontent.com/attachment/0/SaoljwoKCpk AABtrvl01/Part%204%20-%20Architectural%20Acoustics%20- %20handout.pdf?nmid=213800995 5.) wikipedia.com

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