#SOUND REFERENCE FREE#

Ideally the pressure residual intensity should be 'zero' but in practice the difference is due to any phase mismatch between channels. Pressure-residual Intensity Index for a given measurement system, is the difference between the indicated sound intensity level and the measured sound pressure level, when exactly the same signal is fed into the two channels of the sound intensity analysing system. Previously known as the phase index or reactivity index - cite Bruel and Kjaer. A high pressure-intensity index indicates that accurate sound intensity measurements will be difficult. In reactive sound fields, the sound pressure may be 20 dB higher than the sound intensity. In a free-field environment the sound pressure = sound intensity so the pressure-intensity index = 0. Pressure Intensity Index is the difference between the sound pressure and the sound intensity, a good guide to the quality of the measurement - also known as Lk and PI Index. Pressure Gradient : under sound intensity pressure gradient PI Index : under pressure intensity index Phase Index : under pressure intensity index Note : instantaneous intensity is the product of instantaneous acoustic pressure and instantaneous particle velocity. Instantaneous Sound Intensity Definition (IEC 802-01-10) acoustic energy flow rate in the direction of propagation per unit area normal to the direction of propagation. Instantaneous Sound Intensity is the intensity at a specific instant in time and point in a sound field.

#SOUND REFERENCE FREE#

Sound Intensity Related Terms - listed alphabeticallyĪctive Sound Intensity is the propagating part of a sound field, producing a net flow of sound energy, predominant in the free sound field.Įffective Sound Intensity is the root-mean-square of the instantaneous sound intensity, over a given period of time. Sound Intensity Levels are measured with a sound intensity probe to establish both the sound pressure and the particle velocity levels - more details. See also our sound level calculations page and the IEC Definition of Level Sound Intensity Level (L I) uses the 10 log equation, so, as a rule of thumb:ġ0 dB = a factor of 10 in sound intensityĢ0 dB = a factor of 100 in sound intensityĤ0 dB is a factor of 10000 Sound intensity Level is also known as the SIL Sound Intensity Level Formula, Li = 10 log (I/I o) dB, where I is the sound intensity in W/m² and I o is the reference sound intensity of 10 -12 W/m², converting the watts per square metre levels into the more manageable range of 0 to 140 dB as the following list demonstrates.ġ40 dB = 100 W/m² (watts per metre squared)Ġ dB = 0.000000000001 W/m² = 10 -12 W/m² the threshold of hearing

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