Identifying Noise Sources with Sound Source Surveying Equipment

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Our company was subcontracted by Nippon Expressway Research Institute Co., Ltd. (NEXCO RI) to research effective ways to identify road traffic noise sources utilizing sound source surveying equipment.

What is Sound Source Surveying?

Sound source surveying is a surveying technique that allow us to effectively identify complaint causing sources of noise by adopting traditional sound source surveying equipment to road traffic noise surveying.

Complex sound field environments surround highways.

  • Sky-borne sounds wrap around sound barriers that are equipped to elevated bridges from above.
  • Structural sounds are generated by main bridge bodies.
  • Noise from adjacent roads reverberates off of structures.  Etc.

Overview of Sound Source Surveying Equipment

Microphone Array

Microphone Array

Front-End Processor and Measuring Computer

Front-End Processor and Measuring Computer

  • The sound source surveying equipment (manufactured by Brüel & Kjær, owned by NEXCO RI), consists of a 42ch microphone array arranged in a radial pattern, a front-end processor used to store the noise data, and a measuring computer used to control the equipment and analyze the measurement data.
  • Identifying noise generating sources using conventional techniques required a great number of noise level meters, analyzers, and personnel. High elevation work was also required for bridge areas. However, using this sound source surveying equipment method, we can obtain similar results in a safer and more effective manner.

Sound Source Surveying Examples

Using this sound source surveying method, we can easily identify sources of noise.

Identifying joint sounds.

Identifying joint sounds.

Leak sounds from points where sound barriers are not equipped.

Leak sounds from points where sound barriers are not equipped.

  • Visualizing noise sources enables us to identify points where measures are required, thus allowing us to implement effective protective measures.
  • Furthermore, when measures are taken, it allows us to estimate noise reduction levels beforehand.

Sound Source Surveying Measurement Principle (Beamforming Method)

This measurement principle is called the beamforming method. It is a technique that allows us to detect in which direction the signal summation is greatest by placing numerous microphones even with each other, and then correcting the temporal difference Δt against signals measured by multiple microphones. From this, we are able to pinpoint the direction of arrival.