We encounter sound every day but exposure to excessive noise can have serious consequences for our health. Hearing loss is one of the most common work-related injuries.

To protect you and your colleagues, good ear protection is vital. In this article, we cover:

• What sound is
• How it is measured
• Why good quality sound measurement is so important
• What you should focus on when selecting ear protection

What is sound?

Sound is the vibration of air. Sound makes the air around us move. This movement or pressure variation in the air spreads out.

Sources of sound include vibrating vocal chords, the wires in a piano or the prongs of a tuning fork. These vibrations are experienced by us as sounds and expressed in decibels (dB).

Consequences of hearing damage

Hearing damage is irreversible and can cause tinnitus, hearing loss and problems with communication. This can impact your body and mind; it can cause tiredness, stress, sleep disorders, loss of concentration, increased blood pressure, isolation (withdrawal from social situations) and even heart problems. As a result, noise can destroy more than just your hearing. This makes it incredibly important to protect your hearing against noise.

Damage to your hearing cannot be cured, but you can protect against it. In noisy settings, it is essential to wear your ear protection 100% of the time.
Even not wearing it for a short while drastically reduces its effectiveness and increases the risk of hearing damage. If you have already suffered hearing damage, it is hugely important to ensure adequate (sound) rest to avoid exacerbating the problem.

However, you must also ensure that you do not have too much or too little attenuation from your ear protection:

• Too little attenuation
  • Irreversible damage due to hearing loss
  • Reduced focus, which results in lower productivity
• Excessive attenuation
  • Inadequate awareness of speech, environmental and warning sounds, which increases the risk of accidents
  • The ear protection will be worn less, meaning you are not protected adequately.

How is sound measured?

Doubling rule for decibels (dB0

Noise pressure doubles with every increase of 3 dB(A). This means that 83 dB(A) is twice as loud as 80 dB(A). A few examples:

• Two machines each emitting 100 dB(A) together produce 103 dB(A)
• Four machines of 100 dB(A) together produce 106 dB(A) (103 + 3 = 106 dB(A))

The difference between db(A) and dB(C)

Decibels are measured with different filters, depending on the type of sound.

• dB(A): An A-weighting takes account of the sensitivity of the human ear and is used for everyday sound measurements.
• dB(C): The C-weighting is used to measure peak sound levels and gives a greater weighting to lower tones.

Tone level in Hertz

The frequency of sound, measured in Hertz (Hz), determines the tone level: the number of times per second (frequency) that the vocal chords vibrate, for example. Humans can hear frequencies of around 20 Hz (low tones) to 20,000 Hz (high tones). Our ears are most sensitive to mid-tones.

Reading sound cards

• Frequencies: On the horizontal axis, frequencies are given in Hz, with low tones on the left and high tones on the right.
• Intensity: On the vertical axis, the noise levels are given in dB. Higher values indicate louder sounds. The greater the value, the louder the volume.

120-140 dB is the known ‘pain limit’ and the threshold for unpleasant volume, although this varies from person to person.

Harmonised European norm EN 352

Ear protectors help to reduce exposure to damaging sound and fall within the highest risk category III of Regulation 2016/425 EU on personal protective equipment (PPE). This is because ear damage impacts on human well-being and is irreversible.

What does the fact that this is cat. 3 mean for the prevention adviser? What else must be regulated with these products...

EN 352 is a group of norms regarding performance requirements and testing methods for many types of ear protectors, including passive and electronic ear protectors.

3 things you should know about this norm:

1. The norms from EN 352 are amended as part of a periodic review process and harmonised after publication in the Official Journal. One of the most important changes is that manufacturers are now encouraged to develop products that are suitable for employees exposed to low/moderate sound levels, without excessive protection. Therefore, the conformity assessment has been modified: instead of minimum octave band test frequencies (125 Hz to 8000 Hz), minimum values for high (12), average (11) and low (9) frequencies are now met, based on the mean minus 1 standard deviation. SNR details are also reported on the basis of this mean minus 1 standard deviation.
2. The acoustic properties of ear protectors are measured and reported according to guidelines from EN 13819-2. These guidelines support the general requirements of the EN 352 series of norms which are set specifically for ear protection. The acoustic performance of attenuation is tested with the aim of setting the ‘Real Ear Attenuation at Threshold’ for ear protection; this is also known as the REAT-test.
3. EN 352:2020 Part 3 specifies how wearable ear protectors should be tested and states that all loose earmuffs must be tested and approved with the carrier on which they are used.

Want to know more about these norms and the three above points? Download the infographic.

Download the infographic

Action levels and limits

There are action levels and limits for sound exposure in the workplace to prevent hearing loss.

One-off exposure to an intensive impulse or long-term exposure to noise above 80dB can damage hearing.
The upper limit is the maximum permissible sound exposure level for an average working day (8 hours), with the exception of peak values (impulse dB(C)).

• From 80 dB(A), ear protection must be provided and employees must be informed and trained
• From 85 dB(A), ear protection is mandatory
• With exposure to 87 dB(A), the employer must take immediate action:

The sound level, after correction for the use of ear protection, must never exceed this limit. Employees must also have an annual medical check-up if they are exposed to levels higher than 87 dB(A) in the workplace, instead of every 3 years for exposure to over 85 dB(A) and 5 years for exposure to over 80 dB(A).

How do you choose the right hearing protection?

You can't simply say that one ear protection device is better than another, as it all depends on the attenuation levels. The best ear protection is the device that:

• Protects you correctly
• Is comfortable enough to be worn for a full working day
• Allows you to maintain full contact with your environment

Step 1: The importance of good sound measurement

Good quality sound measurement is the basis of effective ear protection and the correct filter choice.

A good sound measurement includes:

• A measurement of all relevant situations
• Recent information (sound measurements must be recent and be representative of the current workplace and situation)
• Clarity about the exposure time of employees
• Frequency-specific information

A simple sound measurement can lead to insufficient or excessive attenuation, which may put safety in the workplace and your hearing at risk.

Step 2: Different types of hearing protection

There are various types of ear protection. There are passive and active ear protectors:

Passive ear protection attenuates the sound due to the materials from which it is made. The efficiency of the ear protection depends on the sound level. Passive ear protection is effective for high pitched sounds, such as alarms.

• Earplugs: Come in various styles, such as disposable, reusable, push-to-fit and banded ear protectors. Disposable earplugs are handy for one-off use, while reusable earplugs are more cost-effective for the long-term as you can use them up to 100 times and they are easy to clean. Push-to-fit earplugs are easy to fit and offer a good seal, while banded earplugs are handy because they can be worn around the neck when they are not being used.

• Earmuffs: With various wearing options, such as a headband, neckband or hanging versions. The choice depends on personal preference and the workplace environment.
• Customised hearing protection (otoplastics): Otoplastics are custom-made earplugs that are produced based on an impression of the ear canal.

Active ear protectors have a built-in electronic system. This system detects a low noise through a microphone, and amplifies and transmits it to a loudspeaker in the device, and vice versa. This helps to control the sound within the ear protector.

• In-ear: Level-dependent earplugs which allow noise through at a safe level, but block damaging noise when it exceeds a certain level.
• Over-ear: Ear protectors with two-way communication or wireless communication accessories which allow employees to communicate safely while they are protected from damaging noise.

Step 3:  Setting the right protection for each situation

When choosing ear protection, it is important to take account of various factors:

• Attenuation & protection: Choose ear protectors with the right attenuation to match the noise levels to which you are exposed. Sufficient attenuation but not over-protected. Over-attenuation results in inadequate awareness of speech, environmental and warning sounds which, in turn, increases the risk of accidents. This may lead to the ear protectors being worn less frequently too, thus reducing the level of overall protection.
• Used in combination with other PPE: Make sure that the ear protectors are compatible with other PPE that you must wear and that, together, they still meet the requirements of the norm.
• Fit check: Make sure that the ear protectors fit properly in order to provide the best protection. (refer to article on Face-Fit tests)
• Comfort & ergonomics: Choose ear protectors that are comfortable, otherwise you may avoid wearing them.
• Situational awareness & communication: Consider how important it is to be able to hear ambient sounds. If this is important, you should choose active hearing protection.
   

Did you know that: 40% of employees choose the wrong type of ear protection and/or wear it incorrectly?*

*This is apparent from HSE study report RR720 ‘Real world use and performance of hearing protection’.

Download the selection guide here

Would you like expert advice?

You can go to Vandeputte for advice or even for a quality sound measurement.

No recent sound measurements?
We can make an appointment to determine the relevant measurement points and analyse specific situations.
We can then plan a sound measurement.
The various methods for calculating filters will be included:

• SNR (Single Number Rating)
• HML (High Mid Low)
• Frequency band analysis (most accurate option)

The result of this is:

• Detailed sound report
• A summary of all measurement results
• A clear interpretation and analysis of the gathered data

If you wish, we can also provide a customised filter calculation, when we will determine the right filters and ear protectors for every situation in your company.
 

Do you have recent sound measurements?
Then we can use these to evaluate current product selection or propose new products for each situation.