Sound sense

Citation

Loughlin, C. (1999), "Sound sense", Sensor Review, Vol. 19 No. 3. https://doi.org/10.1108/sr.1999.08719caa.001

Sound sense

Sound sense

Keywords Sensors, Ultrasonic

When technology advances to the point where we can start to imitate nature then we can be optimistic about our chances of success.

For example the silk created by a spider to form a web is stronger even than our most advanced synthetic fibres, and its structure, with both spiralling and longitudinal elements, leaves aramids such as Kevlar firmly in the shade. In this issue we look at recent advances in ultrasonic transducers and sensing techniques. Many of these new techniques are based around Continuous Transmission Frequency Modulated (CTFM) ultrasonic waveforms which we have only recently been able to create and process in real time. Bats on the other hand have been doing it for thousands of years.

Personal experiments with ultrasonics over 20 years ago gave very disappointing results. We could generate a pulse and time the period of its echo. We even achieved a modest level of precision in distance measurement with micrometer adjustment of our "optical bench" calibration rig. However as soon as the sensor system was aimed at the real world the results became very unreliable and large solid objects would routinely "disappear" when destructive interference rendered them invisible.

Fortunately Professor Leslie Kay (our Guest Academic Editor for this issue) came to our rescue with his ultrasonic transducers for the blind (also used in the Polaroid camera range finder) and our own efforts were swiftly consigned to the waste bin. The Polaroid range finder used multiple frequencies to overcome many of our monotonous difficulties; however it is only now that we are able to generate, and more especially process, a whole spectrum of frequencies, that very significant progress appears to be becoming possible.

These new techniques allow us to see with sounds and obtain 3D images at near video frame rates. The main problem however is that while we are now able to obtain good images, we are still not yet as proficient at interpreting them as our capped crusader friends.

In this issue we have two papers that deal specifically with CTFM techniques. The first is by Professor Leslie Kay and details his work which is largely aimed at assisting blind people, while the second by Professor Phillip McKerrow and Neil Harper (using Kay's sensors) describes progress made in the automatic characterisation of plant types. It is interesting that blind people using these same ultrasonic transducers are able to obtain a much better "picture" than can currently be obtained automatically using computers. This has direct parallels with the worlds of natural and artificial vision and further underlines the sophistication of biological processors.

Our third ultrasonic research paper by Professor Lindsay Kleeman takes a very different approach for the very different task of guiding a mobile robot. In this the emphasis is changed to create a system that is designed from the outset for automatic analysis and to provide the quantitative data required for navigation.

Ultrasonics, once the cheap and cheerful alternative to vision, is now worthy of more diverse application. Add to this its use for applications such as paint thickness measurement and composite cure monitoring (David Shepard and Kim Smith, p. 187 in this issue) and you can appreciate just how useful sound can be.

Clive Loughlin