Chapter 33, Problem 1DAA

Occupational Hearing Loss Frequent exposure to loud noise of a particular pitch can cause loss of hair cells in the part of the cochlea that responds to that pitch. People who work with or around noisy machinery are at risk for such frequency-specific hearing loss. Taking precautions such as using ear plugs to reduce sound exposure is important. Noise-induced hearing loss can be prevented, but once it occurs it is irreversible because dead or damaged hair cells are not replaced.

FIGURE 33.11 shows the threshold decibel levels at which sounds of different frequencies can be detected by an average 25-year-old carpenter, a 50-year-old carpenter, and a 50-year-old who has not been exposed to on-the-job noise. Sound frequencies are given in hertz (cycles per second). The more cycles per second, the higher the pitch.

FIGURE 33.11 Effects of age and occupational noise exposure on hearing. The graph shows the threshold hearing capacities (in decibels) for sounds of different frequencies (given in hertz) in a 25-year-old carpenter (blue), a 50-year-old carpenter (red), and a 50-year-old who did not have any on-the-job noise exposure (brown).

Which sound frequency was most easily detected by all three people?

Summary Introduction

To determine: The sound frequency that was most easily detected by all three people.

Introduction: Hearing refers to the perception of sound. The loudness of the sound is measured in decibels. The frequency of the sound is measured as a number of wave cycles per second or hertz. This determines the pitch of the sound, which is directly proportional to hertz. The range of frequency that can be heard by human ears is 20-20,000 hertz. Continuous exposure to loud noises can damage the hair cells in the inner ear that may result in a temporary or permanent hearing loss.

Explanation of Solution

Refer to Fig. 33.11, “Effects of age and occupational noise exposure on hearing” in the textbook. The graphical representation shows the threshold hearing capacities for the sounds of different frequencies in an average 25-year old carpenter (denoted as blue), a 50-year old carpenter (denoted as red), and a 50-year old who is not exposed to on-the-job noise (denoted as brown). Hearing capacities are measured in decibels and the sound frequencies are measured in hertz. As shown in the graph, the sound frequency that can be heard by all these three individuals is approximately 600 hertz.

Conclusion

The sound frequency of about 600 hertz was easily detectable by all the three people- an average 25-year old carpenter, a 50-year old carpenter, and a 50-year old who is not exposed to on-the-job noise.