The amount of sound a person subjectively perceives as "loudness" is commonly referred to as "volume." Sound is measured in terms of sound pressure and expressed in decibels (dB).

According to standards set by the International Organization for Standardization (ISO), the diagram on the left shows sound pressure values under various conditions. The softest sound a healthy human ear can detect is defined as 0 dB, while 140 dB is considered the upper limit. Exposure to sounds at 140 dB can cause immediate, temporary deafness — and in extreme cases, may even trigger strokes or cardiac arrest.

Even exposure to moderate loud noise can cause a range of health problems, including tinnitus (ringing in the ears), hearing loss, irregular heartbeat, elevated blood pressure, loss of appetite, irritability, reduced work efficiency, difficulty concentrating, and sleep disturbances.

Prolonged exposure to loud sounds leads to auditory fatigue, a condition known as Temporary Threshold Shift (TTS)— where hearing sensitivity temporarily decreases. If the ears are not given sufficient time to recover and exposure continues, this can develop into a Permanent Threshold Shift (PTS) — resulting in permanent hearing loss. People with permanent hearing loss often struggle to recognize certain sounds, especially speech, causing serious communication problems and impairments in daily life and work.

To protect hearing, national standards stipulate that workplace noise should not exceed 85 dB over an eight-hour workday. For existing enterprises that cannot meet this standard immediately, a relaxed limit of 90 dB is permitted. Additionally, if the exposure time is less than eight hours, slightly higher noise levels are allowed — but under no circumstances should sound levels exceed 115 dB, regardless of exposure time.

The basic rule is that the exposure time shall be halved for every 3 dB increase in loudness.
According to this rule, the safe listening time is:
at 85 dB 8 hours
at 88 dB, 2 hours,
at 91 dB, 1 hour,
at 94 dB, half an hour,
at 97 dB, 15 minutes,
at 100 dB, 7.5 minutes,
at 103 dB, 3 minutes and 45 seconds,
at 106 dB, 112.5 seconds,
at 109 dB, 56.25 seconds,
at 112 dB 28.125 seconds,
at 115 dB 14 seconds.
(You can refer to the left diagram for examples of common activities and their associated sound levels.)

Important:
Hearing damage is irreversible. We strongly recommend wearing hearing protection whenever you are in an environment with potentially harmful noise levels.

Which Is More Likely to Cause "Hearing Loss," Music, or Noise?

Surprisingly, if the sound pressure level is the same, music and noise are equally capable of causing hearing damage.

However, noise — being unpleasant, chaotic, and unpredictable — tends to cause more physical and psychological stress compared to music, which is organized and harmonious.

In simple terms, noise is any unwanted sound.
For example, a beginner’s violin practice might sound painful, while a professional’s performance on the same instrument is enjoyable. The frequencies being produced might be similar; what differentiates music from noise is the relationship between those frequencies.

This idea dates back to the ancient Greek mathematician and philosopher Pythagoras, who discovered that pleasant sounds correspond to simple ratios between two frequencies (e.g., 3:2 or 4:3), forming harmonious intervals.
By contrast, complex, non-reducible ratios (e.g., 201:388) create dissonant, harsh sounds — what we perceive as noise.

Working in an industrial setting exposes you to many different types of hazards. One of these is hearing loss due to prolonged exposure to high decibel noise. Unfortunately, many people with hearing loss are under the mistaken impression that noise and work are two sides of the same coin, so you have to live with it.

It couldn't be more wrong; hearing impairment results from prolonged exposure to too much sound. If you're willing to follow some life-changing habits, you can safely maintain your hearing. This way, you can enjoy things like listening to music, having trouble-free conversations with family and friends, and listening to your children or grandchildren laugh.

Industrial noise is mainly constant mechanical noise. Machinery and equipment of the same type produce the same amount of noise, so the number of machines running determines the overall noise level. Even if it isn't deafening, the cumulative dose of constant noise can be powerfully damaging to hearing because of prolonged exposure over an uninterrupted period of time.

The point is because there is no way to actively reduce the noise level or reduce the normal eight-hour working day, you must be stuck in this noisy environment day after day for years and years. It would help if you had a pair of earplugs that are easy to use, effective in reducing noise to a safe level, and comfortable and effective in protecting your hearing.

Foam Material: Straight Earplugs, Bullet-Shaped earplugs, Multi-Ringed Foam Earplugs
The foam material has a good noise reduction rating. If foam earplugs can fit tightly in the wearer's ear canal, they can provide excellent noise reduction. However, single-sized products cannot create a good seal with different-sized and shaped ear canals. Thus, the manufacturers of foam earplugs have developed a formula (minus 7 divided by 2) to calculate the actual noise reduction rating achieved with foam earplugs. Another problem with foam earplugs is that they rely on the foam's expansion force to fill the ear canal. The ear canal deforms as people move about or talk, which causes the earplugs to loosen then slowly slip out, resulting in sound leakage.

Silicone Material Multi-Ring Earplugs
Multi-ring silicone earplugs have double or triple rings. Typically they a small aperture audio restrictor to reduce the sound volume inside the ear canals. It is akin to looking at the sun through a pinhole. The soft round rings of the multi-ring silicone earplugs deform easily. The earplugs fit the ear canal without the forceful ejection feeling of the foam earplugs. The smooth surface does not irritate the delicate ear canal skin as foam does, so it feels good to wear. The audio restrictor port also provides a degree of canal ventilation, which improves from the foam earplugs. However, fixed-sized and shaped silicone multi-ring earplugs do not fit people with different canal sizes and shapes.

Foam-Filled Headband Earmuffs
Headband earmuffs must be fully cover the ears and fit snugly to the head to create an effective noise isolation seal. The tight fit requires considerable pressure and is often painful for the wearer. The earmuffs are not airtight, resulting in a severely uncomfortable feeling of heat. When used as intended, earmuffs provide excellent sound isolation. But the downside is that they are bulky and not very comfortable to wear.

The earplugs can come loose and require frequent manual adjustments. The earmuffs are bulky and stuffy. Causing many industrial workers not to wear these protective devices, creating their hearing deteriorations as they work.

ACS has been promoting hearing protection for over 26 years and has worked with world-renowned DJs, singers, musicians, and bands from the UK, Europe, America, and Asia and supply the UK police, military and industry with hearing protection earplugs. Here's how we think about industrial noise and how we approach our products.

Whether it's noise or music, as long as the volume is the same, the chance of hearing damage is the same. However, the human ear has different sensitivities to different frequencies of sound, so different frequencies with the same loudness will not cause the same hearing damage. Because of this phenomenon, you can't use the average loudness of the entire frequency range when you deal with noise. You must also evaluate the measurements from different frequency bands to find the best countermeasure.

There are many noisy machines in a factory, just as there are many speakers at a concert. The noise from industrial machines is like the music from musical instruments, with some machines producing low-frequency noise and others making high-frequency noise. The same volume of music and noise has an equal chance of damaging people's hearing. Therefore, we will use ACS PRO custom earplugs similar to those used by the world's top musicians during live performances to meet workers' hearing protection needs in industrial environments.

The work "custom earplugs" use the PRO 20, PRO 26, PRO 27, and PRO 31 filter models, of which the PRO 20 and PRO 26 are also used in music earplugs. The PRO 20 and PRO 26 are also used for musical earbuds because the frequency curves of these PRO filters are just right for some of the noise reduction needs of music and industrial environments. Remember when the same frequency in different ratios can determine whether it's noise or music?

This is one of the most common questions we receive.

First, unless you were born deaf or have a medically defined hearing loss (legal deafness), you will always hear some sounds. Human hearing begins at 0 dB — the faintest sound detectable — and 140 dB marks the threshold where sound becomes damaging. Decibels are measured on a logarithmic scale, meaning every 3 dB increase doubles the sound energy. The difference between 0 dB and 140 dB represents a 100-trillion-fold range in sound intensity.
Given the incredible sensitivity of human hearing, it’s impossible to completely eliminate all sound unless one is deaf.

Second, while excessive noise can cause significant physical and psychological stress, we still need to hear certain sounds, even in noisy environments.
Imagine wearing a pair of "super earplugs" that block out 99% of sound. The factory would feel as quiet as a library. However, if a production machine malfunctions and emits an unusual noise, you might miss it entirely. You would only realize something is wrong when the machine stops completely — by then, the damage could be severe, not just a minor issue.

Hearing is also critical for communication with coworkers, receiving instructions from supervisors, and detecting alarms or warning signals from machinery.
Therefore, total sound isolation is not the ideal goal for earplugs.

Additionally, sudden and complete loss of auditory input can cause serious physical and mental discomfort in normal-hearing individuals.
The best earplugs are those that balance noise reduction — protecting your ears from harmful sound levels — while still allowing you to hear important sounds and maintain situational awareness.

In the past, the way to eliminate noise was to block sound from entering your ears, using fingers, paper, cloth, foam earplugs, or foam-filled earmuffs, but the basic concept was all about blocking.

Most of the time, the sound we hear comes from a mixture of sources. However, foam cannot finely control the sound frequencies that pass through it, and if it is worn properly, most of the sound is blocked, and only a small portion can pass through. The earplugs must be removed to communicate with others, and the complete lack of protection causes hearing loss.

We need to hear some of the sounds at work, and barrier products really don't meet this need. The line manager is a perfect example. There are so many machines on the production line, responsible for so many different steps that each machine's output has to be just right every day. However, a factory cannot have all machines running perfectly every day.

The supervisor has to go to the machine that has a problem and talk to the employees to determine the problem. Therefore, neither he nor the employees can wear "blocking" earplugs, which must be removed to communicate. ACS PRO filters will reduce harmful elements and allow you to hear a clearer and safer sound.

The illustration shows the difference in effect between (blocking and filtering).

The Order Process for Custom Earplugs and links to the product page for each model