If possible supply the following information:
1. Obtain the noise level of your equipment in db or request an acoustic engineer to visit your site and get measurements.
2. The amount of reduction desired or the noise target at a specific location relative to the noise source e.g. 85 dBA at 1 metre directly in front of fan outlet and/or inlet.
3. Maximum allowable pressure drop. The difference in pressure between any two points in a gas flow.
4. The air flow properties - flow rate, density, temperature, etc.
5. Available space and geometry and orientation of connections. Size and type of connections and hole pattern required.
6. Environmental conditions for material and finish of silencer.
Decibel (dB) is a logarithmic unit used to express the ratio between two values of a physical quantity, often power or intensity. 0 dB upward towards the threshold of pain, about 120-140 dB. As examples: the sound level in the average residential home is about 40 dB, average conversation is about 60 dB, typical home music listening levels are about 85 dB, a loud rock band about 110 dB, and a jet engine close up could be 150dB.
Sound Power Spectrum calculations are then determined by a sound engineer by measuring air flow rates, static pressure, fan type and speeds. Sound pressure levels are theoretical values, calculated from the sound power level data and are quoted at a specified distance i.e. 1, 1.5, or 3 metres.
You can think of the sound power spectrum as a sound recipe: take this amount of that frequency, add this amount of that frequency etc. until you have put together the whole, complicated sound.
These must then be corrected to suit the local environment at site. Abbreviated to dBA, or dBa, or dB(a),
The dB(A) sound pressure level is used to describe the noise level of many items of noise emitting from machinery. However, published dB(A) sound pressure levels should be used for comparative purposes only; they are not designed to reflect actual installed noise levels. The assumptions that are used to calculate the dB(A) are rarely replicated in real life situations and, therefore, published dB(A) values will not necessarily represent the actual noise levels that may be experienced on site.
Example: Excessive noise levels emulating from a fan
The fan actual db could be 95db and has to be reduced to say 85db or less.
In some situations equipment may not yet be installed so information needs to be obtained from the manufacturer.
FAN: db(a) without acoustic treatment may have:
- A open discharge and needs a silencer to achieve 85db
- Ducted air inlet – break out noise needs to be considered i.e. to be below 85db(a)
- Breakout noise through fan casing could be a issue
Breakout noise is an undesirable sound that is caused by the transmission of sound through the walls of a duct, building or other enclosure
- Sound levels generated by the electric motor running e.g. cooling fan noise
If noise needs to be reduced further e.g 75dba the fan may need an inlet silencer or additionally an enclosure for the complete fan. (See below enclosure considerations)
A silencer is a passive noise abatement device that is typically placed on the inlet or outlet of a noise producing piece of equipment. It allows the air or other gas to flow freely while providing a reduction in sound levels. There are many types and configurations that can be designed.
With over 35 years of experience in acoustical and other related areas, Accord Corporation now has been acquired by C-Mac industries. C-Mac management can now offer you the same service with guaranteed performance and results. Accord Accoustics sets the standard for design experience, manufacture and speed of installation.
C-Mac provides a number of services, primarily in the role of assisting Project Engineers, Company Engineers, Architects, Safety Officers and Factory Managers on the feasibility, design, & manufacture and installation of acoustic performance improvements on standard built and specialty built products for fans, turbines, compressors, blowers, vent silencers for gasses and steam installations. Accord Acoustics enjoys considerable recognition for its expertise in the design, manufacture and installation of quality acoustic products along with providing short lead times.
With the introduction of C-Mac's internal, mature quality assurance system and documented procedures, Accord Accoustics can achieve an even higher quality standard and record keeping systems. Staff ownership of C-Mac also brings a new level of customer service.
C-Mac and Accord Accoustics independantly have built up expertise and goodwill over many years suppling expert service to industry, commercial and architectual areas, as a reliable and safe supplier. Industry and manufacturing demand special designs for solving problems as situations vary enormously from simple enclosures for fans, motor muffs for electric motors to silencers for venting problems. Standard products are not always suitable for a particular problem, designed and purpose built products give the best results.
The combined manufacturing facilities of C-Mac and Accord Corporation provide a comprehensive manufacturing, fabrication & machining facilities with experienced engineering staff, whom ensure strict quality control on all manufactured products, either standard or purpose built. Accord Accoustics offer a full site installation service with all site work being carried out and supervised by experienced and well trained staff. Our Design Engineers and Draftsmen with many years of hands on manufacturing experience are available to assist in identifying your company’s real requirements.