26 Acoustical Absorption

acoustical absorption

Acoustical absorption is used in a wide array of settings and applications.  It is used to control echo, reduce the noise level in a space, make it easier to understand speach, and control focusing.  We now offer a Free Room Acoustics Analysis (noiseexpert.com/free-room-analysis/).  Just enter your project informaton and we will get back to you with an evaluation of the room dimentions, room finishes, reverberation time, direct and reflected noise paths, and the location of acoustical treatment.

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25 Vibration Control


Vibration is a disturbance that is put onto a system. Causes of vibration can be categorized as: continuous, impulsive, and intermittent.

Accelerometers (made of piezoelectric material) are used to measure vibration. Accelerometers gives off a small voltage when they are moved. This voltage is magnified and processed by a signal analyzer – generally in a computer.  The system is calibrated using a shaker. Calibration is performed by connecting the accelerometer to a calibrated shaker that moved up and down at a specific frequency and amplitude.

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24 Sound Isolation

Noise isolation is an acoustical issue we regularly confront. The two primary methods for noise to be transmitted is airborne and structure-borne. Airborne sound sources pass sound by the air which causes the partition (wall or floor ceiling) to vibrate.  The vibration is transmitted and produces noise on the other side. Airborne sound sources include: speech, TV (assuming the unit is not vibrating the partition), stereos, animals, etc.

Structure-borne sound is transmitted from a source vibrating the partition (wall or floor). The vibration of the partition produces sound on the other side. Examples of structure-borne sound sources include: sound from walking on a tile or wood floor, mechanical units (such as a roof top HVAC), plumbing in walls, etc.

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23 Noise Control Basics & Acoustical Product Directory eBook

Our eBook – Noise Control Basics & Acoustical Product Directory eBook is now available on at Amazon for $2.99.

If you get the book please let me know if you have any comments or questions. I would like to build on this each year and make it a practical resource so that people can solve many of their own acoustical problems.

Here is the table of contents:

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22 T60 Reverberation Time

While analyzing an area containing an excessive amount echo or the noise buildup that is too high, reverberation time analysis is often used. Reverberation time is a measure of the time noise remains in a space soon after it is produced. Particularly, reverberation time pertains to the time needed for noise in a space to fall 60 dB following it being turned off.

The preferred reverberation time in a space depends upon its size, together with its use. For example, with talking, a short reverberation period is desired. Should the reverberation period be too long, a person listening will hear noise from more than one word at the same time and the speech will be garbled and not easily understood. Alternatively, for music in a space with a prolonged reverberation period, the musical notes blend collectively which is much more pleasing than dried lifeless noise. So how the area is used has a great deal to do with what reverberation period is most attractive.

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21 Arizona Road Noise Study

I’m going to discuss traffic noise evaluations. Whenever a street is extended, moved, altered, or another one is constructed and there are homes, schools, hospitals, places of worship adjacent, etc, a sound study is needed. The study looks to check whether sound mitigation should be installed.

Sound walls are the typical noise reducing measure utilized to reduce traffic. In a few places, reduction from RAC (rubber asphalt concrete) is permitted. You can move the street up, down or to one side or another but that does not commonly produce sufficient noise reduction. Now and again were sound alleviation is justified and sound walls are not plausible, purchasing properties or enhancing outer surface of a house is done. By and large by enhancing the windows.

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20 Acoustics (Noise) Basics

This blog is a definition of some of the terms I have been using in previous blogs and that I will use in future blogs.

Sound Pressure Level
Sound, or noise, is the term given to the variations in air pressure of which are capable of being heard. Tiny imbalances in atmospheric pressure is the thing that is measured by a sound level meter. Because humans can detect changes in atmospheric pressure over a huge range, sound pressure is measured on a logarithmic scale in decibels (dB). Noise means “unwanted” sound.

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19 Theatre Acoustics

Noise Expert (acoustical engineers) recently completed an evaluation of a theatre located in Prescott, Arizona.  The challenge was that they wanted to preserved a barrel vaulted ceiling.  The ceiling is not steeply sloped – the focal point is several feet below the floor.

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17 Road Noise for Hotels and Condos

Noise Expert has recently evaluated the exterior construction of a few different buildings being constructed near busy roads or highways. The buildings were proposed hotels and condominiums.

Architects, developers and builders can reduce traffic noise impacts by adjusting the site plan, architectural design, construction methods, and using barriers.

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16 Worker Noise – OSHA Noise Testing

Measuring worker noise exposure is the most important part of a workplace hearing conservation and noise control program. It helps identify work locations where there are noise problems.  It identified who may be affected and where noise mitigation should be applied.

OSHA (Occupational Safety and Health Administration) noise exposure testing is conducted by putting a dosimeter on a worker during their entire work day.  The noise exposure is then computed.

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14 Cell Tower Noise Evaluation Phoenix

Noise Expert (acoustical engineers) is evaluating the noise radiating from an existing cell tower.  The primary noise sources are the air conditioner units mounted to the equipment storage buildings.

The goal is to determine the noise levels from the air conditioning units at closest residences.  At the closest residences, there are many other noise sources including: traffic, residential air conditioning units, and aircraft.

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13 Office Building Sound Transmission Testing (FSTC)

Noise Expert (acoustical engineers) measured the Field Sound Transmission Class (FSTC) for seven different walls in a Lockheed Martin office building.  The building was going to be remodeled and some of the rooms were going to have sensitive activity that required an FSTC 50.

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12 Office Building Roof Top Mechanical Equipment Noise

Noise Expert (acoustical engineers) was asked to evaluate the mechanical noise from a rooftop HVAC system located directly above an open office space in Chandler, Arizona.

The low frequency noise levels were very high in the office spaces below the roof top unit.  The ductwork takes an abrupt 90 degree turn under the roof in duct that is too small for the volume of air being moved.  Hence, the air velocities are very high and cause low frequency rumble.

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