![]() ![]() Do we just want to measure the dB SPL - if so probably just need a SLM connected to the appropriate microphone and coupler.Whichever coupler you use (and headphones) will determine what RETSPL you use to convert dB SPL to dB HL.įigure 2 - examples of microphones and couplersįigure 2 - examples of microphones and couplers that might be used to measure audiometer output for calibration purposes.ĭepending on what it is you want to measure you will also need an appropriate measureing device: If you want to calibrate other headphones you may need a B&K 4153 coupler that has a flat plate adaptor for super-aural headphones. If you are measuring free-field presentation then you will need a free-field microphone on your sound-level meter, if you are calibrating an audiometer with TDH39/49 supraural headphones then a 6cc ear simulator such as a B&K4152 with a 1" pressure microphone. ![]() * RETSPL = reference equivalent threshold sound pressure levels - see below.įigure 2 gives examples of the sort of microphones/couplers you might need. 2cc coupler, IEC711 coupler, 6cc coupler, Artificial ear, what *RETSPL values will we need. How is the sound delivered (inserts, supra-aural, circumaural or free-field) this will determine how we couple the microphone to the sound production systemĮ.g. Lets think of a basic examples first – calibrating a pure tone sound produced by a particular system: What equipment do we need to carry out calibration? What you want to measure determines the equipment you need and your approach to calibration. Do you need to measure the background noise, distortion, electrical interference etc.Do you need to measure the duration and shape of the signal envelope?.Do you need to measure the frequency of the signal.It is important that you know what you want to know!Īre you simply interested in the level of a pure-tone in dB SPL or: Or if we are carrying out a research project others would be able to exactly replicate what you have done. The type, complexity and features of each device will require different ranges of measurements, but the same principles will apply to calibrating each device.īy following the appropriate standards and calibration procedures we can be sure that audiometers throughout the country (or world) would produce the same thresholds in an individual subject. Need to be able to verify that it is the same as other equipmentįigure 1 - Examples of different types of audiometers that need regular calibration to ensure that they are fit for the purpose of testing hearing.Need to know that equipment is doing what it is supposed to do.Need to know what you are getting/producing.Why do we need calibration?Ĭalibration is a necessary part of using any audiological equipment, whether it is routine equipment such as Audiometers or specialist equipment used for research projects only. Later sections will take you through different types of calibration procedures. This section gives a basic overview of the calibration procedure, concentrating on pure-tone calibration with supra-aural headphones. The the basic skills and understanding to carry out clinic-based calibration of audiometers.An understanding of the different levels of calibration of audiological instruments.An understanding of the basic principles of acoustics in relation to sound measurement.On studying this material and the associated reading/suplementary material you should be able to demonstrate: Following this, the calibration procedures for various types of audiological equipment will be explained along with accompanying practical sessions. The basic principles of calibration will be explained and the scope and purpose of appropriate standards will be described. In this topic you will study some of the basic theoretical and practical principles of calibration of audiological equipment. ![]()
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