How Loud is Too Loud? Part Two: Hearing in Noise on the Job

Key Points

• Hearing in a noisy work environment is not only difficult for those with hearing loss, but for individuals with normal hearing as well, because background noise can cover up the meaning or clarity of speech.
• The brain has two tasks when hearing in noise: separating speech from noise and filling in missed speech cues in words and phrases to create meaning. It uses things like memory and attention to help it along.
• Signal-to-noise ratio (SNR) is the difference between the level of speech and the level of noise. We want the SNR of an environment to be as low as possible. Products like the ListenTALK and the Listen Everywhere system can help to reduce SNR.
• There are several things an employer can do to help reduce noise without employing a noise control engineer. These actions involve simple steps to decrease noise as well as ways to help employees avoid excessive noise.

Hearing in Noise on the Job

Noise-induced hearing loss isn’t the only negative effect of a loud work environment. Having difficulty hearing in background noise isn’t just a problem for people with hearing loss – individuals with normal hearing may struggle as well. These difficulties can slow workflow, and depending on your work environment, may even pose a safety risk. As noted in Part 1, even people with normal hearing thresholds may exhibit difficulty hearing in noise due to damage in the pathway from the inner ear to the brain. It’s estimated that understanding speech in noise effects 26 million adults with normal hearing thresholds (Beck, et al., 2018). In a noisy work environment, it’s likely that a large majority of employees will note difficulty in these situations.

The clarity, or meaning, of speech mainly comes from consonant sounds like p, f, s, and th. These sounds are quite low in volume and high in pitch. It’s these sounds that background noise tends to cover up making it difficult for people to follow a conversation or understand a co-worker in background noise. Add to this a hearing loss, and you have a recipe for disaster. Individuals with un-treated hearing loss often can’t hear these higher pitched sounds as is. When they’re covered up with background noise, understanding gets even more difficult.

When trying to speak in background noise, the brain has two difficult tasks: separating speech from noise and filling in missed speech cues in words and phrases to create meaning. This filling of the gaps can be done with sentence context, visual cues, body language, or the other speech sounds within a word. If we remember from part one, sound comes into the ear canal and is sent to the inner ear. Hair cells within the inner ear then take that sound and send it to the brain. The signal that is sent, however, isn’t just speech; it’s a jumble of sounds for the brain to parse out. It is then that the brain uses things like memory and attention to filter out speech from noise and fill in the gaps of speech masked by the noise. When we think about this in terms of an employee with normal hearing, we know their attention is often split between the task at hand and the individual with whom they are trying to speak. In an individual with hearing loss, the brain needs to work even harder to understand. Some simple and free ways to help individuals hear in noise is to ensure good lighting, closing the distance between speakers, and making sure to face whomever you are speaking to.

We classify the difference between the level of speech and the level of noise as the signal-to-noise ratio (SNR). A 0 dB SNR would mean that speech (the signal) and noise are equal to one another. The higher the SNR, the better the listening environment. For example, average conversation is around 50 dB. If we have a background noise level of 85 dB, that is a -35 dB SNR – not a prime listening situation. If speech is amplified to 70 dB and the noise is dampened to 60 dB, a +10 dB SNR – a much better situation for speech understanding. Products like the ListenTALK system and the Listen Everywhere system can help to reduce SNR. These products would bring a speakers voice directly to the employee’s ear reducing distance. By bringing speech directly to the ear, background noise is completely bypassed, making speech easy to understand.

Noise Conservation Measures

In terms of noise control to help with hearing conservation, there are several things an employer can do to help reduce noise without employing a noise control engineer. These actions are called “administrative controls” and include easy actions to decrease noise as well as ways to help employees avoid excessive noise.
The first thing one can do is to determine the greatest source of noise. Is there loud music or chatter, like in a sports bar? Is it loud machinery? At the source, one should make sure that all employees are using machinery and other devices properly and that all equipment is well maintained.

Noise can also be dampened in its path – as it moves through space from the source to the individual. One way to do so is to have sound-absorbing material around the source of noise. This can include carpeting, foam pads or spray, felt or cork. An example of a good use of these materials would be carpeting in an office with loud chatter or using foam pads around a noisy machine. Insulated walls or other structures can also be used to isolate noisy machines or equipment and protect multiple people at once.

Employees’ access to noisy environments should be limited to when they absolutely need to be exposed. This can be achieved in many ways such as isolating noisy machinery, placing signs or warnings to indicate levels of high noise, or even shifting work schedules to limit the amount of time each individual is in the noisy environment. Employers should also ensure that employees in loud environments have rest periods or time spent away from excessive noise. In our sports bar example, a well-dampened break room with carpeting and insulated walls can help give employees a break from the loud noise of the bar.

Employees may also use hearing protection devices that come in non-electronic and electronic versions. Beyond the cost-effectiveness of the nonelectronic types of devices, there are several other factors in choosing appropriate hearing protection devices. Some types of devices are outlined below:

While we want devices to be comfortable in the ear, the looser the fit the less effective the device will be. While softer ear plugs are more comfortable, harder plastic custom devices are better at attenuating loud sounds. Additionally, softer disposable devices need to be replaced far more frequently than harder plastic ones. In situations where employees need to engage in conversation while still being protected, active electronic devices may be more appropriate. Devices should also be convenient and available. For custom devices that aren’t disposable, a carrying case is useful to ensure that employees always have access to noise protection. Conveniently placed dispensers may be helpful to make sure disposable devices are always available.

Appropriate insertion is also an important factor. When beginning to use hearing protection devices at your workplace, a training on proper use and the importance of noise protection is helpful to ensure hearing conservation measures are optimal.

While hearing protection devices are a great idea, there are some things that limit their effectiveness. In terms of the disposable foam devices, some extremely loud sounds can pass through this foam. An airtight seal is also needed with all devices to keep sound from getting through any gaps in the fit. Overall, these devices aren’t perfect, but along with the workplace adjustments mentioned above, effective noise reduction and hearing conservation can be easily achieved in your place of work.