AS 4241-1994 pdf free.Acoustics – Instruments for the measurement of sound intensity – Measurement with pairs of pressure sensing microphones.
AS 4241 specifies the requirements for sound intensity instruments, comprising sound intensity probes and processors, which detect sound intensity by pairs of spatially separated pressure sensing microphones. These instruments, and others employing ditferent detection methods, are still the subject of deielopment.
Sound intensity instruments have two main applications. The first is the investigation of the radiation characteristics of sound sources. The second is the determination of the sound power of sources, especially in situ, where sound intensity measurement enables sound power determination to be made under acoustical conditions which render determination by sound pressure measurement impossible.
AS 4241 applies to instruments to be used for the determination of sound power in accordance with the requirementsof ISO 9614-1 and ensures well-defined performance for instruments used in other applications.
Specifications and tolerances are based on current instrument technology and on typical industrial requirements for dynamic capability index.
Requirements for the verification of performance of probes and processors are written in terms of type tests, A scheme for periodic verification, serving as the basis of the periodic recalibrations required in many countries, is given in annex A.
The primary purpose of this Standard is to ensure the accuracy of measurements of sound intensity applied to the determination ot sound power in accordance with ISO 9614-1. To meet the requirements of that standard, instruments are required to analyse the sound intensity in one-third octave or octave bands, and optionally to provide A-weighted band levels. They are also required to measure sound pressure level in addition to sound intensity level to facilitate the use of the field indicatorsdescribed in ISO 9614-1.
This International Standard only applies to instruments which detect sound intensity by pairs of spatially separated pressure sensing microphones.
The requirements are intended to reduce to a practical minimum any differences in equivalent measurements made using different instruments, including instruments comprising probes and processors from different manufacturers.AS 4241pdf download.