Sound Quality

Reducing noise & vibration has long been an aim for the development engineer, and in many cases, levels have been reduced so that many products report very similar results.

 

It’s now becoming clear that it’s not just level that counts, but also the quality of the sound from the machine. Is it rough? Does it sound tinny? Does it rattle?

 

These issues were identified by the automotive industry years ago, and now the sound of a car is as important as the trim level, or even performance. Driving a car is a combination of sensations, of which the sound quality is becoming more important. Are you going to buy a luxury car when the door goes ‘clang’ when you close it?

 

And it’s not just cars. Domestic appliances such as washing machines and lawn mowers will just as likely be chosen for their sound quality as their ability to perform their primary function.

German company HEAD acoustics, based in the university city of Aachen, have been ahead of this game (sorry) for more than ten years. Starting with binaural recording manikins, the company’s range now extends across recording and playback systems, and advanced binaural analysis software.

 

However, sound quality is not just about recording stereo signals and playing around with them, as some competitive ‘sound quality’ systems seem to think.

 

The human hearing mechanism is very powerful, and to harness this power for analysis of complex acoustic stimuli requires special recording and playback capabilities.

The powerful HMS III HEAD Measuring System features 24bit recording technology, and Windows XP/Vista software for set-up and storage of recordings. By using a patented combination of analog and digital equalisation, unprecedented dynamic range is possible.

 

Storage of 24bit data to disk (including tacho data) is via USB interface, and two HEADs can be synchronised for

four-channel recording to disk. The files can then be directly accessed by the ArtemiS software, or exported to other analysis systems..

 

ArtemiS is a native XP/Vista application, developed from the ground up, not just ported from Unix.

 

With full integration in Microsoft Office 2003/2007, sound quality and other analyses are easier than ever before, with playback of filtered signals through the HPS IV 24bit Playback System, featuring electrostatic headphones..

 

ArtemiS can run as a stand-alone system, or alternatively, it can be installed either on the host notebook itself, or on the new portable SQlab III notebook based system, which will accept inputs from microphones, accelerometers, HEADs, tacho probes, strain gauges, CANbus interfaces etc., making a flexible multichannel system.

...and for the more impecunious, check out NoiseBook, which features a subset of ArtemiS functionality, while retaining data compatibility, and ease of use.

 

The unique MHS II headset sports miniature microphones for low-cost binaural recording, as well as playback through the integrated headphones, using USB connection to a notebook.

 

Record binaural signals to disk, and using the NoiseBook software, perform FFT/octave analysis as a function of time or rpm, order analysis, and compare signals in real-time. You can even filter the signals interactively with one or two filters, to estimate the effect of particular components, just like the full-blown

ArtemiS. A database module also allows searchable archiving of recordings, test data, images, documents, etc for fast retrieval and comparison.

 

NoiseBook is already finding favour in troubleshooting applications, and even in car dealerships, for analysing and archiving customer returns, caused by squeaks and rattles.

 

The latest version of NoiseBook also supports direct USB connection of the HMS III digital head, so there’s no excuse for not getting into sound quality!

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