Manufacturer: KOKEN LTD.
Model: Silence 70 And 71

Safer, more comfortable.

EARPLUGS

1. Silence 71 (Corded) – Free Size

Material: Polyurethane (PU synthetic resin – foam type).

2. Silence 70 (Uncorded) – Free Size

Material: Polyurethane (PU synthetic resin – foam type).

These are foam (sponge) type earplugs that are very soft and provide a comfortable feeling against the skin.
How to use: Roll (compress) the earplug with your fingertips, then insert it into the ear canal. There, it will slowly expand and fit perfectly to the shape inside the ear.
There are two product types: Silence 71 (corded) and Silence 70 (uncorded).
■ Earplug Performance: Sound Insulation Value (dB) (Average Value)
NRR 30dB, SNR 34dB

Manufacturer: Bacersha

About NRR and SNR Ratings

These are public ratings indicating the sound insulation performance of earplugs.

• NRR (Noise Reduction Rating): Rating certified by EPA (US Environmental Protection Agency).
• SNR (Single Number Rating): Rating based on JIS T 8161-2 standard (Japan).

Rule: The larger these numbers, the higher the sound insulation performance (noise protection capability).

About Sound Insulation Value (Sound Attenuation)

• The sound insulation value is a figure indicating the ability to block sound.
• This is an estimated value indicating how much ambient noise can be reduced when wearing hearing protection.
• This value differs depending on the frequency of the sound.

TO PREVENT NOISE HAZARDS…

● Harmful effects of noise

• Various sounds exist around us (Table 1). “Noise” is the general term for unpleasant sounds or unwanted sounds for anyone.
• For workplace noise environments, to prevent hearing damage, the targets for control are excessively loud sounds (85dB(A) or higher).
• When noise occurs, it causes effects on the human body such as:
  Psychological effects: Irritability, frustration…
  Physiological effects: Nausea, high blood pressure…
• This leads to reduced work ability, decreased attention span, and becomes a cause of unexpected accidents.
• Furthermore, if continuously exposed to noise, the hair cells (sound receptor cells) inside the ear will be destroyed, leading to Noise-induced hearing loss.
• For acoustic trauma caused by instantaneous loud explosions, early treatment can help recover, but hearing loss due to noise deafness is basically irreversible.
• Noise-induced hearing loss is a condition where hearing is gradually lost due to long-term exposure to noise (Table 2). In the early stages, the patient will not hear sounds higher than normal conversation (frequency around 4000Hz), so it is often not noticed in daily conversations. If you feel like you have “gotten used to the noise,” the situation may have become incurable.
• Noise-induced hearing loss tends to occur more easily as the sound pressure level gets higher and the exposure time gets longer. It is necessary to continuously maintain a comfortable working environment by lowering sound pressure levels or shortening exposure time.

● Noise Countermeasures

• Basic measures to prevent noise harm are environmental improvements, such as: eliminating noise sources, enclosing (isolating) noise sources, or sound absorption treatment.
• However, in reality, noise treatment is very difficult. If noise levels cannot be lowered as desired, it is possible that workers cannot avoid exposure to high noise levels.
• In such cases, hearing protection devices (such as earplugs, earmuffs) are the solution to prevent noise exposure at the individual level.

Legal Regulations:

According to the “Guidelines for Prevention of Noise-Induced Hearing Disorders” issued by the Ministry of Health, Labour and Welfare of Japan:

• It is necessary to conduct noise environment measurements at the workplace.
• In places with equivalent noise levels of 85dB (A) or higher, it is mandatory to improve the environment while simultaneously wearing hearing protection devices.

Practical Tip:

• Pay special attention if you have to shout to be heard by someone about 1m away.
• In that case, the noise level is considered to have reached 85dB (A) or higher.

Risk (%) of noise-induced hearing loss by years of exposure

(Excerpt from: “Workplace Noise Management”)