Event Name IEEE & ITEE Evening Lecture by Dr Keith Adams on How is Environmental Noise Perceived and how should it be Measured in spite of Established Practice?
Start Date 1st Aug 2012 6:00pm
End Date
Duration N/A

Title: How is Environmental Noise Perceived and how should it be Measured in spite of Established Practice? [pdf]

Speaker: Dr Keith Adams

Time and Date: 6:00pm refreshments for 6:30pm start, Wednesday, 1 August 2012

Place: John Connell Auditorium, Engineers Australia Building, 21 Bedford Street, North Melbourne


Environmental noise, especially aircraft noise is largely incoherent broadband noise, sometimes with the addition of tonal components. The processing of acoustic signals in the human ear is complex with frequency masking and various nonlinear processes present, which cannot be modeled by the simple frequency response of a linear system. Attempts to overcome these defects by focusing on “perception” metrics, successively resulted in algorithms to compute the “effective perceived noise level”, stationary loudness, and time-varying or dynamic loudness. The ratification of a standard for dynamic loudness provides an opportunity to put environmental noise monitoring on a more rational basis.

This talk will focus on the differences in monitoring obtained from the simple frequency weightings, the “perception” metrics and especially the fifth percentile measure of the dynamic loudness algorithm. It turns out that by judicious re-programming of the DSP of a standard outdoor noise-monitoring terminal the various metrics of environmental noise can be simultaneously recorded and compared in real-time. Some aspects of the dynamic loudness algorithm and its DSP implementation will be explained, and its advantages over A-weighting presented in dealing with noise from different types of aircraft combined with background noise. The fifth-percentile of dynamic loudness has much to recommend it as a suitable metric for noise monitoring. As a result of diagnostic testing for the correct implementation of the algorithm, the fifth percentile of the dynamic loudness metric was found to have an interesting special property, which has applications in the identification of certain sounds that do not arise from aircraft.

Psychoacoustics and the related field of soundscapes are in active development. Loudness is only one, albeit one of the most important, of several metrics that go to make up how noise is perceived. The area offers scope for signal processing developers to engage with the phenomena of perception and cognitive psychology.

Speaker Bio:

Keith Adams has been involved with the monitoring of aircraft noise for more than 20 years. He was the first chairman and R&D director of Lochard Ltd, an Australian company set up to provide instrumentation and systems to monitor aircraft noise worldwide. In 2009, Lochard was acquired by Spectris plc and incorporated as a division of Brüel & Kjær under the name B&K EMS.

In recent years there has been growing dissatisfaction about the discrepancy between the standard measurement procedure for environmental noise and human perception of noise. Now semi-retired, Keith Adams has long been in favour of adopting more realistic procedures, which originally were perceived as too difficult or cumbersome to implement in practice. These days, with modern technology, there is no practical barrier to implement whatever is required in accordance with the best available theoretical and experimental knowledge.

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