tools, materials & knowledge for model makers
A weighting sound is the most generally used filter when making overall noise measurements. The attenuation of the sound signal with an A-weighted filter corresponds to the fact that the human ear is not as sensitive to sound of the lower frequencies as it is at the higher frequencies. The A-Weighted Sound Level is a … Read more
There are a number of different community noise criteria measurements, some of which are described below: CNEL = Community Noise Equivalent Level This is used to characterize average sound levels over a 24-hour period, with weighting factors included for evening and nighttime sound levels. Leq values for the evening period (7:00 p.m. to 10:00 p.m.) … Read more
Room acoustic modes occur at frequencies at which sound waves in a room resonate (in the form of standing waves), based on the room dimensions. The acoustic modes will “colour” the sound, ie enhance certain frequencies and dull others. Therefore, the standard modal approach for designing a room with good acoustics is to create as … Read more
There are a number of different types of acoustic chambers and rooms. Some are defined very specifically and others more loosely. These rooms are mainly used by noise and vibration measurement specialists. Acoustic chambers and rooms are quite specialist rooms to design, build, operate and maintain. Often the design of these rooms will be done by … Read more
A term generally used to describe aerodynamic noise produced when a gas flows within a duct or when the gas exits the duct, hence flow noise. This is a typical problem observed in the exhaust systems of internal combustion engines and high engine rotational speeds and hence high gas flow rates. There is a balance … Read more
There are a number of different ways to attenuate the sound waves propagating down a duct (eg air intake, exhaust system) and I thought it would be good to list these different acoustic filter elements, how they work and their effect on the sound waves. Absorptive Duct Absorption within ducts is used to break up … Read more