Sennheiser HD 25 HDM PRO User Manual

Once the headphones have delivered 30% of the permitted daily dose,
the flash rate increases from 3 seconds to 1 second.

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This faster flash rate alerts the listener that they have already been exposed
to a significant amount of their daily dose, and prompts them to consider if
the monitoring level should be adjusted for the remaining of the listening
session.

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Indication that HDM

Whenever HDM®Pro is about to increase the level of attenuation,
the Red and Green LEDs will flash together.

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Ambient Noise:

To ensure the best listening experience it is important that you are working
in a suitable environment without significant amounts of ambient noise. If
you can’t clearly hear the reproduced sound from your HDM
headphones due to ambient noise, you should take action to reduce the level
of ambient noise or consider moving to a quieter place.

PRO is actively managing levels:

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Pro enhanced

Quick Start Guide for

HD 25 HDM®Pro Enhanced

Headphones

Important:

HD 25 HDM
media production staff who use headphones to monitor sound for several
hours a day. An individual person should use a single set of HD 25 HDM®Pro
Enhanced Headphones per working day. The HD 25 HDM®Pro Enhanced
Headphones are important tools to protect staff from damaging sound
exposure.

The Hearing Dose Management
to reproduced sound via the headphones. Other sources of sound contribute
to your daily noise exposure, and so LimitEar Ltd is unable to guarantee
compliance with the regulations in isolation. HDM®Pro is effective in helping
to protect against Noise Induced Hearing Loss from reproduced sound.

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Pro Enhanced Headphones have been developed for professional

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function of HDM®Pro only controls exposure

Sennheiser Solutions is a global initiative created by Sennheiser with the aim to
standardise the approach local subsidiaries and partners take in producing small
volume custom solutions that compliment the existing Sennheiser product range.

www.sennheiser.co.uk/solutions

[e-mail] Phone [phone]

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HDM Pro

Introduction

The HD 25 HDM

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Pro Enhanced Headphones are standard Sennheiser
HD25 professional headphones fitted with the HDM®Pro Hearing Dose
Management® monitoring and protection device. This device is fitted to the
headphone’s cable and is designed to maintain the maximum audio fidelity
while ensuring the listener’s reproduced sound exposure remains within
the limits of health and safety regulations. These regulations place legal
responsibilities on the employer to ensure their employees are not subjected
to damaging levels of sound exposure.

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Pro provides the three levels of protection to assist compliance with the

HDM
EU and UK Noise at Work (NaW) regulation 2005.

• Peak reproduced sound levels are limited to a maximum of 118dB.

• Reproduced sounds between 100dB and 118dB are reduced to 100dB by a

fast acting attenuator, in approximately 500ms.

• The device monitors the accumulated reproduced sound exposure and

applies level control management, ensuring the daily hearing dose produced
by the headphones remains within the regulations. The regulations specify
an average sound pressure exposure per day. HDM

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Pro monitors and

controls the sound exposure on a rolling 24 hour period.

Green LED initially

double flashes every
10 seconds to indicate
charging and low
battery.

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PLEASE

CHARGE FOR

3 HOURS

BEFORE FIRST

USE

Blue LED indicates the

unit is connected to a
power source.

Once it is charged, Green LED
single flashes every 10 seconds.

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It will take between 3-6 hours for a full charge dependent upon the current
battery state. A full charge will last for up to 7 days of use. Use a standard
Micro USB lead with any USB power supply or computer.

When in use, if the Green or Red LED start to double flash, it indicates that
charging is required and 24 hours of use remains.

Operation

Normal professional ‘safe practice’ rules apply, before you connect
headphones to any equipment:

1. Remove headphones from your ears.

2. Ensure that the volume control of the headphone amplifier is at the
minimum setting.

3. Connect the headphones to your equipment, put them on and increase the
volume control to a comfortable level.

Once you begin to hear audio, the Green LED will start to flash at approx 3
second intervals, indicating that HDM

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Pro is monitoring the signal.

During your listening period keep an eye on the display. The greater the ratio
of Red to Green flashes, the greater the level of the incoming audio playback.
Monitoring at louder levels reduces the permitted listening duration, and the
LED ration indication should be used to make judgements about appropriate
playback levels.

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QUIET:
Below 80dBA

IDEAL:
80-85dBA

LOUD:
85-90dBA

TOO LOUD:
90-95dBA

EXTREME:
95dBA

No action required

Optimum listening level

Reduce volume when
possible

Reduce volume soon to
preserve dose

Reduce volume urgently
to preserve dose

If the Red LED flashes every 10 seconds this indicates that
the unit has been used within the previous 24 hours and
contains some residual dose.

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Thoughtful users of HDM

Pro unplug or turn down the volume when they are not

actively listening to ensure the maximum level is available to them when it’s needed.
If the battery is allowed to completely discharge the unit will power down and

place 14dBs of attenuation to the signal to provide you with some basic protection.