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Technical Considerations

BUILDING CHARACTERISTICS

An examination of most public buildings will reveal some or all of the following factors which may need Printacall's expertise.

BUILDING ACOUSTICS AND PA SYSTEMS

Optimum sound conditions for partially deaf people with or without hearing aids require minimum echo or reverberation. Hearing aids actually compound the problem due to the sensitive omnidirectional microphone in the hearing aid. In most public locations the walls are acoustically hard and some ceilings are also prone to echo. Most floors are "hard" but given an average audience may provide minimal echo. Carpets and soft seating are the preferred option.
Louder is not better. Multiple lower level speakers are more effective for the hearing impaired than the usual louder two front of house type that can exacerbate existing acoustic problems. These may include reverberation time, poor frequency response and excessive echo.
Hearing loops can only perform as well as the quality of the audio input provided to them. Omnidirectional microphones pick up much more of the acoustic limitations of a building than the preferred close working directional microphones.

INTERFERENCE

Hearing Aids can be affected by magnetic interference that can occur when the aid is operating on the "T" switch, normally in the form of a low frequency (100Hz or 150Hz) buzz radiated from sub-stations, some dimmers and some cabling. This can be improved somewhat by boosting the level of the Hearing Loop, thereby improving the signal to noise ratio.
The "T" switch will pick up this buzz regardless of whether an induction loop or a neckloop (with the infra-red or FM system) is used. Note that it is not Hearing Loops that are affected by interference, but the "T" switch on the hearing aid which picks up the buzz from the other sources.

LOOP LAYOUT ISSUES

A factor which is not always understood is that a narrow null zone of low signal level occurs directly over the loop cable location (when installed in the floor) and under the loop cable location (when installed in the ceiling).
Printacall designs aim to ensure this effect is minimised for the user, but some professional building designers, architects etc sometimes designate loop cable locations that take no account of this effect.

METAL LOSSES - EFFECTS OF STEEL AND OTHER METALS

Buildings with concrete slabs include large amounts of steel reinforcement. Steel framed floors also incorporate significant amounts of steel, as do steel framed ceiling grids. Over time, as standards change, the amount of steel required in new buildings tends to increase. 
The steel results in dramatically lower loop level and poor frequency response for the user unless considered as part of the overall hearing loop design. 
Moving the loop cabling away from the steel only partially reduces the effect of the steel on the Hearing loop System.
Printacall addresses these issues at the design stage to ensure clear sound through the loop system.

LARGE AREAS

Where substantial areas need to be covered, Printacall can design multi-loop systems to cover large areas. In some cases, Printacall may recommend a Wide Area FM solution, such as in sport or entertainment arena sized venues. Printacall also supply these systems as required.

SPECIAL PURPOSE CUSTOM DESIGNED LOOPS

Call Printacall to discuss your particular problems or concerns. A one off custom design may be just what you need for your situation.

 

SOUNDFIELD VS HEARING AUGMENTATION

Is Soundfield an alternative solution for Hearing Augmentation?


BASIC HEARING LOOP CHECK LIST

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DISABILITY DISCRIMINATION ACT – DDA

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• Hearing Loops assist meeting the requirements of the DDA

• Hearing Loops should be included in the Disability Action Plan

• Hearing Loops reduce the risks of DDA complaints

BUILDING CODES OF AUSTRALIA - BCA

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CURRENT STANDARDS

• Requiring a minimum of 80% coverage for Hearing Loop Systems

• Compliant with the Disability Discrimination Act

 

 



 

 


The Hearing Loop