Engineering and the Environment, University of Southampton

Knowledge and understanding
Having successfully completed the module, you will be able to demonstrate knowledge and understanding of:

• General two-port description of transducers including their electrical, mechanical and acoustic properties.
• Electroacoustic analogies.
• Modification of a transducer's electrical behaviour by its mechanical environment and vice-versa.
• Equivalent models for moving coil loudspeakers.
• Loudspeaker and microphone performance in terms of frequency response, directivity and distortion.
• The influence of a baffle, a closed box and a tuned enclosure on the response of a loudspeaker.
• The principles of pressure and pressure gradient microphones.
• The frequency limits due to equalisation and diffraction.
• The division of a microphone's response into acoustic, mechanical and electrical parts.
• The principles of operation of condenser, ceramic, electret and dynamic microphones.
• Microphone calibration methods.

Cognitive (thinking) skills
Having successfully completed the module, you will be able to:

• Read, understand and interpret the literature relating to loudspeaker and microphone design and operation.
• Recognise and select appropriate techniques for the analysis of electroacoustic problems.

Practical, subject specific skills
Having successfully completed the module, you will be able to:

• Understand product specifications for electroacoustic transducers.

Key transferable skills

• Interpret manufacturers' catalogues.

The aims of this module are:

• To introduce a general two-port description for acoustic transducers.
• To discuss the principles of operation and practical use of both loudspeakers and microphones.

• To develop a unified approach to the analysis of transducers.

General Theory (6 lectures)

• Description of electrical, mechanical and electroacoustic systems as two-port networks, coupling, analogies, acoustic networks.

Loudspeakers (9 lectures)

• Equivalent models for moving coil loudspeakers, and relationship to practical loudspeakers. Loudspeaker performance in terms of frequency response, directivity, and distortion, and their measurement. The influence of an infinite baffle, closed box and tuned cabinets. The horn equation, simple solutions and application.

Microphones (9 lectures)

• Pressure and pressure gradient principles, diffraction. Diaphragm dynamics and transduction mechanisms, hence complete frequency responses for various microphone types. Methods of calibration. Directivity of first order microphones, diffuse field response.

2 lectures a week.

Lectures include a combination of presentation, and the discussion of the properties of examples of practical loudspeakers and microphones handed round in class.

Two tutorials are arranged to review the material and revise for the examination.

Home study of the notes provided in the lectures. Students are encouraged to read supporting texts and papers and a booklist is provided.

Secondary text

Fundamentals of Acoustics
3rd Edition 1982
2nd Edition 1962, L E Kinsler
A R Frey
A B Coppens
J V Sanders, John Wiley
0471094102 pbk
0471029335 hbk

Electroacoustics, Microphones, Earphones and Loudspeakers, M L Gayford, Newnes-Butterworth

Condenser Microphones and Microphone Preamplifiers, 1982, Anon, Bruel & Kjaer Naerum
(No ISBN)