Press release
11.02.2009 - Holte
Transmission using light: Optical microphone for industrial and medical applications
Industrial facilities, EMI/EMC laboratories, magnetic resonance imaging – the optical microphone from Sennheiser is ideal for areas in which other microphones are only partly suitable or cannot even be used at all. With the launch of the MO 2000, the audio specialist has expanded its portfolio with a new type of transducer that represents acoustic signals on the basis of variations in light intensity. And now, with the introduction of the IAS MO 2000 Set product version, Sennheiser is also presenting the first – and currently the only – microphone on the market to be certified for use in potentially explosive atmospheres.
 The optical microphone from Sennheiser for industrial and medical applications. It consists of an acoustic-optical microphone head and a central unit. |
“The optical principle means that the microphone head and the electronics can be located far away from each other,” said product manager Kai Tossing, explaining the advantages of the optical microphone. “What is more, the microphone head doesn’t contain any metal; it is made of a plastic material that can withstand exposure to aggressive substances such as gases, salts and humidity. No electric current flows through the microphone head. All these features make our optical microphone the perfect candidate for applications in which communication or measurements are required under the most difficult conditions.” |
Medical applications
In the medical field, the optical microphone is ideally suited for use in magnetic resonance imaging (MRI), for example, in order to maintain contact with the patient during MRI scans or to provide active noise cancellation. Due to its metal-free and current-free design, the microphone head does not interfere with the imaging process and is itself not influenced by the strong magnetic fields inside magnetic resonance imaging equipment.
Measuring technology
The optical microphone also benefits from its metal-free and current-free design when used in measuring applications, as it does not influence the magnetic field. In EMI/EMC laboratories, for example, it functions like an “artificial ear” on a mobile phone without distorting the measurements.
Potentially explosive atmospheres
 The IAS MO 2000 Set product version for potentially explosive atmospheres and outdoor applications includes weather protection for the optical microphone. |
A special version of the optical microphone is available for use in potentially explosive atmospheres and for outdoor applications. The |
Operating principle of the optical microphone
In the optical microphone, light from a light-emitting diode (LED) is directed onto a reflective diaphragm via a fibre-optic cable (transmitter fibre-optic cable). The diaphragm reflects part of the light into a receiver fibre-optic cable. If the diaphragm is moved by sound signals, the reflected light beam is deflected, with the result that more or less light is coupled into the receiver fibre-optic cable. At the end of the receiver fibre-optic cable, a photodiode converts the light intensity variations into electrical signals.
The Sennheiser Group, with its headquarters in Wedemark near Hanover, Germany, is one of the world’s leading manufacturers of microphones, headphones and wireless transmission systems. The family-owned company, which was established in 1945, recorded sales of over €395 million in 2007, 83% of which were generated abroad. Sennheiser employs almost 2,000 people worldwide, around 55% of whom are in Germany. Sennheiser has manufacturing plants in Germany, Ireland and the USA, and is represented worldwide by subsidiaries in France, Great Britain, Belgium, the Netherlands, Germany, Denmark (Nordic), Russia, Hong Kong, India, Singapore, Japan, China, Canada, Mexico and the USA, as well as by long-term trading partners in many other countries. Also part of the Sennheiser Group are Georg Neumann GmbH, Berlin (studio microphones), K + H Vertriebs- und Entwicklungsgesellschaft mbH (Klein + Hummel studio monitors, installed sound) and the joint venture Sennheiser Communications A/S (headsets for PCs, offices and call centres).
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You can find all the latest information on Sennheiser by visiting our website at www.sennheiser.com, or by contacting:
Sennheiser electronic GmbH & Co. KG
Press & PR • Edelgard Marquardt
Am Labor 1 • 30900 Wedemark
Germany
Tel.: +49 (0)5130 600 329
Fax: +49 (0)5130 600 295
E-mail: edelgard.marquardt@sennheiser.com
Optical microphone
Versions and areas of application
MO 2000 Set medical applications, measuring technology, industry
IAS MO 2000 Set* potentially explosive atmospheres,
outdoor applications
Technical data
| Polar pattern | omni-directional |
| Optical fibre | multimode 200/230 µm |
| Frequency response | 20 Hz to 40 kHz (±6 dB) |
| Sensitivity | 15 mV/Pa |
| S/N related to 1 Pa sound pressure | > 50 dB(A) |
| Max. sound pressure | 134 dB |
| Amplification | infinitely variable in the range +/-15 dB, switchable in steps 0 dB, +20 dB, +40dB |
| AF output level | 15 mV/Pa (potentiometer in mid position, switch set to 0 dB) |
| Output impedance | approx. 330 ohms asymmetrical, 660 ohms symmetrical |
| Current consumption | 120 mA |
| Operating temperature range |
microphone: -10°C to +70°C |
*The system IAS MO 2000 Set complies with the requirements regarding intrinsically safe optical radiation according to EN 60079-0:2004 and EN 60079-28:2007. It also meets the requirements of the ATEX Directive on explosion protection, which was documented with the Type Examination Certificate TÜV 07 ATEX 553824 and TÜV 07 ATEX 553825X. This certification allows the IAS MO 2000 SET to be used in potentially explosive atmospheres of Zone 1 (e.g. gas processing plants). The IAS MO 2000 SET has the degree of protection IP 54 (5= protection against dust deposits, 4= protection against splashing water from all directions) and is therefore suitable for outdoor applications.
