ISO 14163 pdf download.Acoustics — Guidelines for noise control by silencers
1 Scope
This International Standard deals with the practical selection of silencers for noise control in gaseous media. It specifies the acoustical and operational requirements which are to be agreed upon between the supplier or manufacturer and the user of a silencer. The basic principles of operation are described in this International Standard, but it is not a silencer design guide. The silencers described are suitable, among others, – for attenuating system noise and preventing crosstalk in heating, ventilation and air-conditioning (HVAC) equipment; – for preventing or reducing sound transmission through ventilation openings from rooms with high inside sound levels; – for attenuating blow-off noise generated by high-pressure lines; – for attenuating intake and exhaust noise generated by internal combustion engines; and – for attenuating intake and outlet noise from fans, compressors and turbines. They are classified according to their types, performance characteristics and applications. Active and adaptive passive noise-control systems are not covered in detail in this International Standard.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 3741 , Acoustics — Determination of sound power levels of noise sources using sound pressures — Precision methods for reverberation rooms. ISO 3744, Acoustics — Determination of sound power levels of noise sources — Engineering methods for free-field condition
3 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply. 3.1 silencer device reducing sound transmission through a duct, a pipe or an opening without preventing the transport of the medium 3.2 dissipative silencer absorptive silencer silencer providing for broad-band sound attenuation with relatively little pressure loss by partially converting sound energy to heat through friction in porous or fibrous duct linings 3.3 reactive silencer general term for reflective and resonator silencers where the majority of the attenuation does not involve sound energy dissipation 3.4 reflective silencer silencer providing for single or multiple reflections of sound by changes in the cross-section of the duct, duct linings with resonators, or branchings to duct sections with different lengths 3.5 resonator silencer silencer providing for sound attenuation at weakly damped resonances of elements NOTE The elements may or may not contain absorbent material. 3.6 blow-off silencer silencer used in steam blow-off and pressure release lines throttling the gas flow by a considerable pressure loss in porous material and providing sound attenuation by lowering the flow velocity at the exit and reacting on the source of the sound (such as a valve)
3.7 active silencer silencer providing for the reduction of sound through interference effects by means of sound generated by controlled auxiliary sound sources NOTE Mostly low-order modes of sound in ducts are affected. 3.8 adaptive passive silencer silencer with passive sound-attenuating elements dynamically tuned to the sound field 3.9 insertion loss, D i difference between the levels of the sound powers propagating through a duct or an opening with and without the silencer NOTE 1 The insertion loss is expressed in decibels, dB. NOTE 2 Adapted from ISO 7235.
4 Specification, selection and design considerations
4.1 Requirements to be specified 4.1.1 In general, the sound pressure level (A-weighted, one-third-octave or full-octave) shall not exceed a specified value at a specified position (e.g. at a work station, in the neighbourhood, or in a recreation room). The permissible contribution from a sound source can then be determined in terms of the sound power level and the directivity index of that source using sound propagation laws and requirements concerning the allocation of contributions to several partial sound sources. The required insertion loss of the silencer is given by the difference between the permissible and the actual sound power level of the source.