Acoustics

**Speed** is the rate of motion, or equivalently the rate of change of distance. Speed is a scalar quantity with dimensions lenght/time; the equivalent vector quantity to speed is velocity. Speed is measured in the same physical units of measurement as velocity, but does not contain the element of direction that velocity has. Speed is thus the magnitude component of velocity. The speed of sound describes the distance such a wave travels in a certain amount of time, it is 330 m/s.

**Frequency** is the number of occurrences of a repeating event per unit time. It is also referred to as **temporal frequency**. The **period** is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency. In physics and engineering disciplines, such as optics, acoustics and radio, frequency is usually denoted by a Latin letter //f// or by a Greek letter //ν// (nu).

  **Wavelength** is the distance between repeating units of a propagating wave of a given frequency. Examples of wave-like phenomena are light, water, and sound waves. The wavelength is related to the frequency by the formula: wavelength = wave speed / frequency. Wavelength is therefore inversely proportional to frequency. Waves with higher frequencies have shorter wavelengths. Lower frequencies have longer wavelengths, assuming the speed of the wave is the same.

**Longitudinal waves** are waves that have same direction of oscillations or vibrations along or parallel to their direction of travel, which means that the oscillations of the medium (particle) is in the same direction or opposite direction as the motion of the wave. Mechanical longitudinal waves have been also referred to as **compressional waves** or **compression waves**. A **transverse wave** is a moving wave that consists of oscillations occurring perpendicular to the direction of energy transfer. If a transverse wave is moving in the positive //x//-direction, its oscillations are in up and down directions that lie in the //y-z// plane.


 * NOTES **
 * Reverberance** is linked to the speed at which sound energy disappears in a room. An unfurnished room with hard surfaces, such as a church, is perceived as being more reverberant than a well-furnished living room.

Room acoustic comfort is an important element of the sound environment concept. The interaction between the person, the room and the activity decides the room acoustic comfort.

Sound transmission, sound absorption, sound reflection and sound diffusion are all aspects of room acoustics.

In many environments where people are present and communicate, high sound levels are perceived as one of the most disturbing factors. High noise levels have a negative effect on us. The reverberation time is decided by: - Added absorption and where it is placed, - The quantity and placing of sound-scattering objects such as furniture, shelves etc. - The size and shape of the room. Clarity of speech is essentially determined by: - Early sound reflections in relation to late sound reflections. - Background noise.

The ceiling’s sound absorbing properties are described in sound absorption classes (A-E) in an international standard. Class A is the highest level of sound absorption. Effective, sound-absorbing ceilings (Sound absorption class A) affect reverberation time, sound level, speech clarity and spatial decay, thus creating good room acoustic comfort.

**NOTES ABOUT PODCAST** Large objects creat large waves, with low pitch, or low frequency waves, on the other hand, small objects creat small waves, but with high picth, or high frequency waves. The sound can be created by compresing and then releasing air molecules, doing this the sounds is created. If the objects producing the sounds is near, the energy is stronger, but if you are futher away from the objects, the energy from the sounds is lower. The acelerated sounds is form when something hits hard, wich creates an inmediate expansive wave wich acts the same way as the sounds waves, but this one have more range, wich means that they loose energy faster. The speed of sound is easy reachable, but while you havent reach it, the waves have time to move thru the air, but if you reach the speed of sounds, the waves compress and explote, wich creates a SONIC BOOM, this means you broke the speed of sound.


 * 1) DB0F0F