Noise reduction, and surveys

Introduction

Sound between 20Hz and 20kHz is audible to humans. Experiencing high levels in this bandwidth can be painful, damaging to the inner ear and your hearing.

Enforced regulations, like Noise at Work Regulations 2005, prevents damage to our health.

We are passionate about making the working and living environment more pleasant. We're not only governed by regulations and legislation, and perform surveys to mitigate high levels of noise for the better of all. We mitigate by design, through vibration control and other mitigation measures. Improving the environment at your work, your home and in the natural environment for your enjoyment.

We start with an assessment, and a report with our conclusions and mitigation measures. But that is not where we finish. Our expetise and knowledge are in vibration, structural dynamics and vibration control to reduce vibration that is the source of noise.

Here are the industries in which we operate:

Automotive, and off-highway vehicles

Our work in the automotive industry mostly involved vibration and noise radiation. Because of the radiation, much of our analysis is transfer path analysis.

What is transfer path analysis?

Transfer path analysis (TPA) is an experimental and a test-based process on a structure of interest. Performed with measurement equipment - a shaker with an impedance sensor (measures both load and acceleration) and microphones. The analysis of the data determines the dominant path of vibro-acoustic energy from a source to a receiver.

In our case weighting the vibration sources, that contribute to the overall noise level, enables us to focus first on the main source contributor.

Through this measurement and analysis method, we can pinpoint the vibration source that contributes the most to the sound levels within the car.

With the advent of the electric car, this area of expertise is very useful, as noise levels within an electric car is much less than that of a conventional car with an internal combustion engine, as an electric car is more silent than an internal combustion engine car, which masks the underlying sounds at lower thresholds within the car.

Marine

As mechanical engineers and acousticians, we admit that our naval architecture knowledge is limited. Yes, we are treasured to mitigatie unwanted sounds in yachts, and valued in mitigating or resolving them from ships.

As there are several sources within a powered sea going vessel, the predominant sources are the propellers and the power units. As the vessel has mainly a steel or aluminium hull, the vibration generated by the two sources becomes structure-borne, and is radiated from the hull throughout the vessel.

Here our experience in space refinement plays a fundamental role, as we must focus on all three areas to find an optimal solution for unwanted sounds.

Read further by clicking the buttons below

Machinery

With industrial machinery, we perform assessments and measurements to establish a transfer path from the vibration to where the noise is emanating. Once identified, we mitigate the vibration source through design, by manipulating the structrual behaviour. Read more on vibration control

Construction

During the Covid-19 pandemic, less people are on the roads and in the cities. Hence, the background noise levels were lower than usual.

With the background levels lower than usual, noise consultants have identified that conventional mitigation measures were often not sufficiently effective during the lock-down. For this reason, more affective mitigation measures are required.

In such cases, we focus on the source. As, on a construction site, the sources come from the construction equipment. We modify and improve the construction equipment, so that the equipment radiates less noise. And the construction site levels stays below the regulations threshold limit.

Residentail and industrial

We perform noise sassessments ain rural, residentail and industrial areas to ascertain the noise levels. These we docuemnt in a report and submit to the local enfircement agency or council. Noise assessments in these areas are usually requested by the local authority for a variety of reasosn.

Highway

High way noise assessments to support and in line with the Design manual for roads and bridges LA 111 ( revised and updated form HD 213/11 and IAN 185/ 15)

Railway

If a new railway is effecting the noise quality in your property, you may be able to get sound insulation installed in your home. Performing a noise survey according to BS 8233:2014, we are able to determine the level of noise break-in to your property.

Aircraft or aviation

Noise is controlled to some extent at airports in the UK. This includes noise limits and restrictions on flights during the night time. Aircraft paths are generally planned to fly over the less populated areas. Some airports operate grant schemes to install sound insulation in affected homes. Contact the airport that affects you to find out if they do have a sound insulation scheme. For more information on aircraft noise, contact the Civil Aviation Authority (CAA), as they motion some airports 24 hours, 7 days a week.

Wind farm & turbine

At 350m the noise generated by a wind turbine is usually between 35 - 45dB(A). This should be limited to 5dB(A) above the background noise for both day- and night-time, remembering that the background level of each period may be different.

A fixed limit of 43 dB(A) is recommended for night-time. This is based on a sleep disturbance criteria of 35 dB(A) with an allowance of 10 dB(A) for attenuation through an open window (free field to internal) and 2 dB(A) subtracted to account for the use of LA90,10min rather than LAeq,10min.

Any sounds other than that of the wind passing over the wind turbine blades could be related to the system within the housing of the turbine alternator, To identify the source, we would conduct signal processing of the recorded data and match it with the vibration content of the mechanical and electrical system within.

During night-time, a fixed limit of 43 dB(A) is acceptable. And is based on a sleep disturbance criteria of 35 dB(A).

We perform assessments and surveys according to ETSU-R-97 and PPS 18.

To read more on mitigation through vibration control, click here.

BS4142 & BS8233

Our most recent project involved that of noise and vibration - structure-borne sound. To give a brief overview of the project, it was for planning permission of a building modification.

An existing building was modified by constructing several flats above the ground floor. The ground floor was occupied by businesses.

These businesses had auxiliary equipment, including industrial extractor fans, compressors and boilers installed at the rear of the premises.

In the council district planning documentation, it stated that the council had a concern about the noise impacting on the future residents of the building. We were requested to perform a noise survey according to BS4142:2019 and BS8233:2014 to assess the impact of the noise on the future residents and propose mitigation actions.

After conducting the noise survey, we provided the customer with a report of our findings, noise levels, the impact thereof and the mitigation actions that could reduce the noise and the structure-borne sound.

Our main objective, other than performing an independent noise survey, was to help the customer and to understand what the enforcement officers at the district council specifically wanted to know.

Communicating with all the parties interested in the outcome of the noise survey, we succeeded to resolve the concerns of both the compressor and the extractor fan.

Our cost efficient mitigation actions comprised of isolating the equipment to lessen the structure-borne sound, and installing a fan with a noise level lower than that of the ambient.