Acoustics_Vocabulary

**Sabine** 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).

**Signal to noise ratio (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.

**Sound absorbers** 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.

**Sound insulation ** 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.

**Sound strength (dB) ** Measured in dB (deciBel). dB is measured at different frequencies.

<span style="font-family: 'Comic Sans MS',cursive;">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. <span style="font-family: 'Comic Sans MS',cursive;">dB(C) (or LpC) particularly focuses on low frequencies and better reflects how a sound is perceived by people with impaired hearing.

<span style="font-family: 'Comic Sans MS',cursive;">**<span style="color: #800080; font-family: 'Comic Sans MS',cursive;">Speech intelligibility ** <span style="font-family: 'Comic Sans MS',cursive;">Speech intelligibility is directly dependent on the level of background noise, reverberation time and the shape of the room. Different methods are used to evaluate speech intelligibility, the most common ones are RASTI, STI and %-Alcons.

<span style="color: #800080; font-family: 'Comic Sans MS',cursive;">**Speech Transmission Index (STI)** <span style="font-family: 'Comic Sans MS',cursive;">Similar to the RASTI method but a more complete form of measuring speech intelligibility by measuring all octave bands in the frequency range 125-8000 Hz.