CHOOSING & USING THE RIGHT BOOM & THROAT MICROPHONE

At one time or another, the safety and/or communications professional will be faced with recommending the correct communication product to a customer or user.  The variety of audio transducers is becoming extensive and in order to recommend the best product for the customer, it would be useful to know something about the main microphones in use today by Special Electronics & Designs Inc. (“SED Inc.”).

Boom Microphones

Boom Microphones:

• Dynamic
• Electret

These further break down to:

• Non-Noise Canceling
• Noise Canceling

For special applications, the Boom Microphones may be available in waterproof and/or low temperature versions.  Please inquire with SED Inc. on availability for your application.

Throat Microphones

SED Inc. Throat Microphones are available for corresponding Dynamic and Electret applications and these are available in Standard (for use to 120 dBA) and Extended Ambient Noise types (for use to 125 dBA).  SED Inc. considers its Throat Microphones to be noise rejecting (as opposed to noise cancelling).

Bone Conducting Microphones

At this time, SED Inc. does not offer Bone Conducting Microphones.

Boom Microphones: Considerations

The Boom Microphone assembly places the microphone close by the User’s mouth, and although this is the preferred microphone arrangement, it is susceptible to some special considerations to ensure optimal performance.

• Protective hoods and plastic suits may displace many competitor’s Boom Microphones due to contact causing frustration to personnel as they attempt to reposition it with glove clad hands. SED Inc.’s gooseneck microphones are designed with this in mind and are very resistant to repositioning by clothing contact.
• Air supplied suits sometimes create wind noise if they have an especially strong airflow directed toward the face and microphone.
• When personnel are wearing a SCBA (Self-Contained Breathing Apparatus), the microphone boom must be long enough to position it at the speech diaphragm/sound port of the SCBA mask.
• Personnel wearing ½ face masks/filters, or SCBA’s only, equipped with an exhalation valve, may choose from a Throat Microphone or a Boom Microphone positioned in front of the speech port when used in conjunction with the SCBA.

Throat Microphones: Considerations

In each of the situations just described, the Throat Microphone is the ideal solution.  Its operation is, however, not ideal in some situations where the User has a muscular or thick neck at the voice box and where the Throat Microphone is positioned.  In these cases, alternatives may have to be considered.  Note that we, at SED Inc., consider our Throat Microphones to be noise rejecting (not canceling) and consider their performance superior in high noise level areas to many products in the marketplace.

Other Microphones: Considerations

Many customers may want to consider an in-the-ear type of microphone and/or receiver and although this area of interest has been great, close attention must be paid by the individual to hygiene, and, in high noise applications this method must be tested to assure its viability.

Bone Conducting Microphones can be very uncomfortable as they press on the crown of the head.  Hair may impede the performance of the Bone Conducting Microphones.

Lapel Microphones are considered unusable because of the ambient noise pick-up.

Which type to use? – Noise Canceling, Noise Rejecting, or Standard

Once the User has determined which style of microphone to use, there are some considerations required to decide which microphone of that group to use – Noise Canceling, Noise Rejecting, or Standard.  One of the most important questions to consider first is “What is the peak ambient noise level?”.

Low Level Noise: Considerations

If the noise level does not exceed 100 dBA, either the Standard or Noise Canceling Microphone may be used.

In situations where a person may be overcome with fumes, a Non-Noise Canceling Microphone may be considered since the potential, of an in-progress accident may be picked up via the open microphone and relayed via the communication system to team mates.  A Noise Canceling Microphone may cancel out these critical tell tales such as laboured breathing, slurred and indistinct speech, a SCBA tank hitting the floor, etc.  (Note: this would not be true of headsets with microphones activated by a PTT (Push-To-Talk) button or VOX.)

The best operation of a Standard Microphone is when it is coupled with a straight amplified system such as that offered by our DMI/DSI intrinsically safe system.

High Level Noise: Considerations

In situations where the noise levels exceed 100 dBA to 105 dBA, a Standard Non-Noise Canceling Microphone should only be considered for special situations i.e., when the operator can use a PTT (Push-To-Talk) button to switch the microphone “off” between spoken passages or use a PTM (Push-To-Mute) button to silence the microphone when it is not required.

Using a Noise Canceling Microphone ensures that worker fatigue is greatly reduced because he/she is not exposed to continuous background noise.

SED Inc. Microphones – Adjustment, Operation, and Care

SED Inc. has been designing and manufacturing Throat and Boom Microphones since 1971.  Care throughout the design and manufacturing stages has always been given to intelligibility in high noise applications.  Recent innovations have allowed SED Inc. to push the ambient noise limits to well beyond 120 dBA.

Boom Microphones

First, the adjustment of the boom is always the same; the microphone is to be adjusted off center at the side of the mouth and within 4mm or ¼” of the corner of the lips.

Adjustment to the side of mouth is very important.  With the microphone off center, as people exert themselves, their exhaled breath will not impinge on the microphone to create unwanted wind noise.  In amplified voice systems, this will cause a very loud “shushing” sound in all headphones of the personnel on the system.  This sound, when added to the voice audio, will mask the desired voice component and will reduce intelligibility in higher ambient noise applications.

In voice actuated (VOX) systems, this will cause the unwanted triggering of the amplifiers, or even worse, triggering of a transmitter and hence the unwanted occupation of the transmission frequency preventing others from transmitting.

It is important to adjust microphones to within 4mm or ¼” of the lips because these microphones are highly efficient noise-canceling devices.  By close adjustment to the lips, we are ensuring that the microphone will “recognize” the voice audio presented to it as the primary sound source and not the incident or ambient noise (which totally surrounds the headset operator).

Throat Microphones

The SED Inc. Throat Microphone, when properly adjusted, and used, can be a pleasure to use compared to many older and competitive products that caused the wearer to feel as if they were being choked, or worse, burned by the carbon-based contact pods.  The key words here are, Properly Adjusted.

First of all, the correct microphone location must be found on the User.  Generally, the microphone should be adjusted high up under the chin and to one side of the voice box.  We recommend the User conduct a test for the best microphone position by using the microphone plugged in without the neck strap attached and having a person at the receiving end evaluating the sound quality and providing the User with feedback.

The User starts by positioning the microphone high up on the voice box while talking to the receiving partner.  The User may try a variety of positions moving back on the neck and away from the voice box.  It will be noted that clarity, and hence intelligibility, will increase but audio level will decrease.  Select the position that provides the best audio level with good intelligibility.

How Audio Quality is affected.

Now attach the neck band or neck strap according to the User’s preference.  The Throat Microphone must be positioned with only light pressure – just enough to ensure the unit will not move during work.  The neckband may be reshaped (larger or smaller) and the neck strap’s length may be adjusted to accommodate the User’s neck profile, after which the neck strap can be unhooked for easy removal.  The neckband should be worn in a manner such that the opening is positioned at the front (leaving the windpipe unrestricted) so that tensing the neck muscles will not cause a restriction of the User’s throat.

Operation is very easy and straightforward.  Just remember to annunciate words clearly.  In high noise situations, this becomes more important since the User is also, most likely, actuating a VOX switched radio or amplifier.  Do not yell or raise your voice.  Unlike other manufacturers, SED Inc. does not reduce the sensitivity of its microphone and/or associated circuitry for high noise use.

Windscreen Replacement

To remove the windscreen, simply grasp the screen on one side, pull outward, and over the microphone end.

To install a new windscreen, gently stretch the windscreen over the end and slide into place.  Some windscreens come with an “O” Ring to hold the windscreen in place.  Once the windscreen has been pulled over the microphone, roll/slide the “O” ring over the foam until it rests behind the microphone sound openings.

Replace the windscreen whenever it becomes soiled or for hygiene purposes.

Written by:  Rolf Eberl