Acoustics_Vocabulary



Shock wave : (also called shock front or simply "shock") is a type of propagating disturbance.

Pitch : is an auditory perceptual property that allows the ordering of sounds on a frequency-related scale. Pitches are compared as "higher" and "lower" in the sense associated with musical melodies, which are coherent successions of pitches. Pitch is a major auditory attribute of musical tones, along with duration, loudness, and timbre.

 Amplitude : is the magnitude of change in the oscillating variable with each oscillation within an oscillating system.

 Beat : is an interference between two sounds of slightly different frequencies, perceived as periodic variations in volume whose rate is thedifference between the two frequencies.

Refraction : is the change in direction of a wave due to a change in its speed.

Reflection : is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated.

Ultrasound:  is cyclic sound pressure with a frequency greater than the upper limit of human hearing.

Flutter echo <span style="font-family: Georgia,serif; font-size: 120%;">: Occurs when noise bounces between parallel surfaces in a room.

<span style="display: block; font-family: Arial,Verdana,Tahoma,Helvetica; font-size: 10pt;"><span style="color: #ed5ed9; font-family: Impact,Charcoal,sans-serif; font-size: 120%;">Noise: <span style="font-family: Georgia,serif; font-size: 120%;"> Unwanted sound. Noise can often be the individual perception of a particular sound, e.g. a background noise.

<span style="color: #ed5ed9; font-family: Impact,Charcoal,sans-serif; font-size: 120%;">Privacy <span style="font-family: Georgia,serif; font-size: 120%;">: Acoustic privacy between working places in open plan offices is expressed with the Articulation Class (AC).

<span style="color: #ed5ed9; font-family: Impact,Charcoal,sans-serif; font-size: 120%;">Reverberation time, ( <span style="font-family: Georgia,serif; font-size: 120%;">T or RT): The time it takes for the sound pressure level to fall by 60 dB after the sound has been turned off. Measuring the reverberation time allows us to calculate the total sound absorption. The reverberation time varies according to the frequency.

<span style="color: #ed5ed9; font-family: Impact,Charcoal,sans-serif; font-size: 120%;">Sabine <span style="font-family: Georgia,serif; font-size: 120%;">: The physicist Wallace Clement Sabine (1869-1919) created in Riverbank, west of Chicago, the well known Sabine formula (T=0,16V/A), showing the relationship between reverberation time (T s), room volume (V m³) and the amount of absorption (A m²).(image): (Sabine's formula)

<span style="color: #ed5ed9; font-family: Impact,Charcoal,sans-serif; font-size: 120%;">Signal to noise ratio <span style="font-family: Georgia,serif; font-size: 120%;">(S/N): Another important parameter influencing speech intelligibility is the background noise level or, more specifically, the signal to noise ratio (S/N). This is the ratio between signal (e.g. speech) and background noise (e.g. ventilation noise). To achieve good speech intelligibility a signal is considered to be at least 15 dB above noise level. For hearing- impaired people the need is even greater; a ratio of at least 20 dB is often referred to. On the other hand, if the signal to noise ratio is much less, or if the signal is lower than the noise, the signal will be partly masked. Thus some privacy can be achieved.

<span style="color: #ed5ed9; font-family: Impact,Charcoal,sans-serif; font-size: 120%;">Sound absorbers: <span style="font-family: Georgia,serif; font-size: 120%;"> Materials and structures with the ability to take up sound energy and convert it into other forms of energy. They improve room acoustics by removing sound reflections, thus reducing the noise and the reverberation time.

<span style="color: #ed5ed9; font-family: Impact,Charcoal,sans-serif; font-size: 120%;">Sound absorption: <span style="font-family: Georgia,serif; font-size: 120%;">Means that sound energy is converted into mechanical vibration energy and/or heat energy. Sound absorption is expressed as the sound absorption coefficient α or the sound absorption class (A-E) according to EN ISO 11654 or NRC/SAA according to ASTM C 423.

<span style="color: #ed5ed9; font-family: Impact,Charcoal,sans-serif; font-size: 120%;">Sound insulation <span style="font-family: Georgia,serif; font-size: 120%;">: The ability of a building element or building structure to reduce the sound transmission through it. The sound insulation is measured at different frequencies, normally 100-3150 Hz. Airborne sound insulation is expressed by a single value, Dn,f,w, Rw or R'w. Impact sound insulation is expressed by a single value Ln,w or L' n,w .Sound pressure level (dB) The pressure variations caused by sound waves in air are called sound pressure. The lowest sound pressure level which can be heard is 0 dB, known as the hearing threshold. The highest level which can be tolerated is called the pain threshold and is around 120 dB.

<span style="color: #ed5ed9; font-family: Impact,Charcoal,sans-serif; font-size: 120%;">Sound strength <span style="font-family: Georgia,serif; font-size: 120%;"> (dB): Measured in dB (deciBel). dB is measured at different frequencies.dB(A) (or LpA) is a single-figure value used to describe the total sound strength for all frequencies in a way similar to the sensitivity of the ear.dB(C) (or LpC) particularly focuses on low frequencies and better reflects how a sound is perceived by people with impaired hearing.