In noise-induced hearing loss, audiogram shows a typical notch at
**Core Concept**
Noise-induced hearing loss (NIHL) is a type of sensorineural hearing loss caused by prolonged exposure to loud sounds, leading to damage in the hair cells of the cochlea. The audiogram is a graphical representation of hearing thresholds, and NIHL is characterized by a specific pattern of hearing loss.
**Why the Correct Answer is Right**
The typical notch in NIHL is seen at 4 kHz, which is a result of the damage to the hair cells in the basal end of the cochlea. This region is responsible for processing high-frequency sounds, and the damage to these hair cells leads to a significant drop in hearing thresholds at this frequency. The basal end of the cochlea is more susceptible to damage from noise due to its location and the type of hair cells present.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the notch in NIHL is not typically seen at 2 kHz. While some individuals may experience a slight drop in hearing thresholds at this frequency, it is not a characteristic feature of NIHL.
* **Option B:** This option is incorrect because the notch in NIHL is not typically seen at 6 kHz. While high-frequency hearing loss is a common feature of NIHL, the specific frequency at which the notch is seen is typically 4 kHz.
* **Option C:** This option is incorrect because the notch in NIHL is not typically seen at 1 kHz. This frequency is more commonly associated with hearing loss due to other causes, such as presbycusis or ototoxicity.
**Clinical Pearl / High-Yield Fact**
It's essential to note that the notch in NIHL is often bilateral, meaning that both ears are affected, and it's not uncommon for the notch to be more pronounced in one ear than the other.
**Correct Answer: C. 4 kHz**