Electroacoustic transducers, such as microphones and loudspeakers, are commonplace in the fields of acoustics and audio and it is important that acoustical engineers have an understanding of the theory and mechanisms of electroacoustic transduction. This module provides the knowledge to understand and predict the behaviour of a wide range of electroacoustic devices, and to relate this to real-world transducer technology.
Aims and Objectives
• To develop a competence in understanding the theory of electroacoustic devices • To establish links between the theory and the real-world application of electroacoustic devices • To develop a unified approach to the analysis of electroacoustic transducers
Disciplinary Specific Learning Outcomes
Having successfully completed this module you will be able to:
- Describe the general two-port description of transducers including their electrical, mechanical and acoustic properties.
- Describe the principles of operation of condenser, ceramic, electret and dynamic microphones.
- Microphone calibration methods.
- Understand and interpret the literature relating to loudspeaker and microphone design and operation.
- Recognise and select appropriate techniques for the analysis of electroacoustic problems
- Understand product specifications for electroacoustic transducers and interpret manufacturers' catalogues.
- Recognise and use electroacoustic analogies.
- Predict changes to the electrical behaviour of a transducer by its mechanical environment and vice-versa.
- Describe equivalent models for moving coil loudspeakers.
- Recognise and use the Thiele-Small parameters
- Discuss loudspeaker and microphone performance in terms of frequency response, directivity and distortion
- Predict the influence of a baffle, a closed box and a tuned enclosure on the response of a loudspeaker.
- Discuss the use of crossover networks in loudspeaker systems
- Describe the principles of pressure and pressure gradient microphones and be aware of the frequency limits due to equalisation and diffraction
General Theory (9 lectures): Description of electrical, mechanical and electroacoustic systems as two-port networks. Coupling. Analogies. Acoustic networks. Reciprocity. Microphone and loudspeaker arrays. Hydrophones. Loudspeakers (12 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. Crossover networks. The horn equation, simple solutions and application, loudspeaker specifications. Power output and mutual coupling. Diaphragm dynamics. Microphones (12 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. Highly directional microphones. Microphone specifications. Laboratory (3 lectures): Estimation of the Thiele Small parameters of a loudspeaker driver.
Learning and Teaching
Teaching and learning methods
This is a one-semester course comprising three 45 minute lectures per week. Lectures include a combination of presentation, the discussion of the properties of examples of practical loudspeakers and microphones handed round in class and a laboratory session. Past exam papers are supplied to aid personal study, feedback and revision. Blackboard is used to allow the lectures and additional material to be disseminated. Students are encouraged to read supporting texts and a booklist is provided.
|Wider reading or practice||30|
|Completion of assessment task||12|
|Supervised time in studio/workshop||3|
|Total study time||150|
Resources & Reading list
Kinsler L.E, Frey A.R, Coppens A .B and Sanders J. V. (2000). Fundamentals of Acoustics.
Anon, Bruel and Kjaer Naerum. Condenser Microphones and Microphone Preamplifiers.
M.L. Gayford. Electroacoustics, Microphones, Earphones and Loudspeakers.
|Exam (120 minutes)||90%|
|Exam (120 minutes)||100%|
Repeat type: Internal & External