Are Sounds Muffled After Exposure to Loud Noise? It May Be Temporary Threshold Shift

Posted on by Hearing Systems

You know that feeling of muffled hearing after attending a concert at White Oak Music Hall or walking by a noisy construction site? This phenomenon is known as temporary threshold shift (TTS), which we review below.

How We Hear

Large concert crowd

To understand TTS, it’s important to understand how we hear.

  • Soundwaves from your environment are captured by the outer ear and travel down the ear canal, which leads to the eardrum.
  • When the soundwave hits the eardrum, a vibration is created, which passes through three tiny bones within the middle ear called the malleus, incus and stapes.
  • This vibration reaches the fluid-filled cochlea in the inner ear, which causes the fluid to move.
  • The movement activates the tiny hair cells that line the cochlea called the stereocilia, creating an electrical impulse.
  • This electrical impulse travels via the auditory nerve to the brain where it is interpreted as sound.

Causes of Temporary Threshold Shift

When you’re exposed to excessively loud sounds, it can bend the stereocilia. The cells can remain this way for several days or even weeks, which is why it takes some time to regain your full sense of hearing. The louder the noise, the longer it will take to recover.

How Loud Is Too Loud?

Sounds over 85 dB can cause TTS or permanent damage to the hearing system. For reference, below is a list put together by the National Institute on Deafness and Other Communication Disorders of the average decibel rating of familiar sounds:

  • Normal conversation: 60-70 dB.
  • Movie theater: 74-104 dB.
  • Motorcycles: 80-110 dB.
  • Sporting events and concerts: 94-110 dB.
  • Sirens: 110-129 dB.
  • Fireworks show: 140-160 dB.

Temporary Threshold Shift Can Be Serious

As the name suggests, TTS is temporary, but that doesn’t mean it isn’t serious.

A single loud concert probably won’t cause any permanent damage to your hearing system; however, repeated exposure can. Repeated episodes of TTS can become permanent threshold shift (PTS).

In most cases, it’s the high-frequency sounds like consonants that are most affected.

Preventing Temporary Threshold Shift

In order to prevent TTS and PTS, you should wear earplugs whenever you’re exposed to sounds over 85 dB.

For more information about TTS or to schedule an appointment with a hearing expert, call Hearing Systems today.