Acoustics

Speed

Rapidity in moving, going, traveling, proceeding, or performing; swiftness; celerity: the speed of light; the speed of sound. The speed of sound is the distance travelled during a unit of time by a sound wave propagating through an elastic medium. In dry air at 20 °C (68 °F), the speed of sound is 343.2 metres per second (1,126 ft/s). This is 1,236 kilometres per hour (768 mph), or about one kilometer in three seconds or approximately one mile in five seconds.



Frequency

Frequency is the property of sound that most determines pitch. It is the number of complete waves in one second. Sounds are generally audible to the human ear if their frequency lies between 20 and 20,000 vibrations per second, but the range varies considerably with the individual. Everywhere in daily life, there are frequencies of sound and electromagnetic waves, constantly changing and creating the features of the visible and audible world familiar to everyone. Some aspects of frequency can only be perceived indirectly, yet people are conscious of them without even thinking about it: a favorite radio station, for instance, may have a frequency of 99.7 MHz, and fans of that station knows that every time they turn the FM dial to that position, the station's signal will be there. Of course, people cannot "hear" radio and television frequencies—part of the electromagnetic spectrum—but the evidence for them is everywhere. Similarly, people are not conscious, in any direct sense, of frequencies in sound and light—yet without differences in frequency, there could be no speech or music, nor would there be any variations of color.



Wavelength

Wavelenght is the distance between one peak or crest of a wave of light, heat, or other energy and the next corresponding peak or crest. The higher the frequency, the shorter the wavelength.



Longitudinal and Transverse

Longitudinals are vibrations parallel to direction of travel. Transverses are vibrations at right angle to direction of travel. Sound is transmitted through gases, plasma, and liquids as longitudinal waves, also called compression waves. Through solids, however, it can be transmitted as both longitudinal waves and transverse waves. Longitudinal sound waves are waves of alternating pressure deviations from the equilibrium pressure, causing local regions of compression and rarefaction, while transverse waves (in solids) are waves of alternating shear stress at right angle to the direction of propagation.

Note:

Vibrations set up invisible waves in the surrounding air. The velocity of any soundwave equals its wavelenght times its frecuency. Amplitude determines loudness. The greater the frequency the higher the pitch of the sound. Signal is a wanted sound, Noise is unwanted sound. Sometimes sound is wanted in spaces, and sometimes its not, and becomes noise. In a concert hall, for example, you want to appreciate the quality of the music and also give people a good experience. <span style="font-family: Georgia,serif; font-size: 120%;">Noise can cause stress, fatigue, make you feel uncomfortable and reduce your quality of life in your neighborhood. <span style="font-family: Georgia,serif; font-size: 120%;">There is more to a building than just the artistic side, it is important to think about the design of the acoustic environment of a building by getting the architectural form and materials right. <span style="font-family: Georgia,serif;">