# Sound Intensity and Threshold of hearing

• gomess
In summary, the textbook equation β= 10log(I1/I2) uses I1 as the threshold of hearing (1.0x10^-12) in most cases. However, in situations where sound intensity is not measured from a human perspective, a different reference level may be used.
gomess
My textbook says that in the equation β= 10log(I1/I2), I1 in most cases is the threshold of hearing (1.0x10^-12). Just out of curiosity, when is I1 not the threshold of hearing?

the reference intensity for zero dB, is 1 pico-Watt/m^2 . I can't hear such faint sounds anymore, especially at the edges of my frequency range. I used to be able to hear 1/8 picoWatt/m^2 ... that's -9 dB ... at 880 Hz.

gomess said:
My textbook says that in the equation β= 10log(I1/I2), I1 in most cases is the threshold of hearing (1.0x10^-12). Just out of curiosity, when is I1 not the threshold of hearing?

Well sound intensity is the measure of a ratio of two sound intensities, when we are discussing the sound intensity experienced by people, then it is useful to set this 'reference' level at the average threshold of human hearing. In any situation when you are not concerned with sound intensity as experienced by people, you might choose a different reference level, it would depend on what you wanted to measure.

Oh okay, i see that makes more sense. I was always wondering why we placed that value as I1, there seemed to be no explanation from my book, it simply stated to do so

I can confirm that the equation β= 10log(I1/I2) is commonly used to calculate sound intensity (β) where I1 is the reference intensity and I2 is the measured intensity. In most cases, I1 is considered to be the threshold of hearing, which is the minimum sound intensity that can be detected by the human ear. However, there are certain situations where I1 may not be the threshold of hearing.

One such situation is when the individual has hearing loss or impairment. In these cases, the threshold of hearing may be higher than the standard value of 1.0x10^-12. This is because the individual's ability to detect sound is reduced due to damage to the ear or auditory nerve. In such cases, I1 would be a higher value than the standard threshold of hearing.

Additionally, the threshold of hearing can vary depending on the frequency of the sound. The standard value of 1.0x10^-12 is for a sound with a frequency of 1000 Hz. For sounds with higher or lower frequencies, the threshold of hearing may be different. This is because the human ear is more sensitive to certain frequencies than others.

Furthermore, external factors such as background noise, distance from the sound source, and individual differences in hearing ability can also affect the threshold of hearing. Therefore, in these situations, I1 may not be the standard threshold of hearing.

In conclusion, while the standard value of I1 is commonly used as the threshold of hearing in the equation, there are certain situations where it may not accurately represent the minimum sound intensity that can be detected by the human ear. It is important to consider these factors when using the equation to calculate sound intensity.

## 1. What is sound intensity?

Sound intensity is the amount of sound energy that passes through a given area in a specific amount of time. It is measured in watts per square meter (W/m²) and is directly related to the loudness of a sound.

## 2. How is sound intensity measured?

Sound intensity is typically measured using a decibel (dB) scale, which compares the intensity of a sound to a reference level. The formula for sound intensity is 10 log (I/I₀), where I is the sound intensity being measured and I₀ is the reference intensity of 10⁻¹² W/m².

## 3. What is the threshold of hearing?

The threshold of hearing is the lowest sound intensity that can be detected by the human ear. It is typically measured at a frequency of 1000 Hz and has a value of 0 decibels (dB). This means that any sound with an intensity below the threshold of hearing will not be audible to the human ear.

## 4. How does sound intensity affect the human ear?

Sound intensity can have a significant impact on the human ear. Prolonged exposure to high sound intensities can lead to hearing loss and damage to the delicate structures within the ear. The threshold of pain, which is the sound intensity that causes physical discomfort, is around 120-140 dB for most people.

## 5. What factors can affect the threshold of hearing?

Several factors can affect the threshold of hearing, including age, genetics, and exposure to loud noises. As we age, the sensitivity of our hearing decreases, leading to a higher threshold of hearing. Genetics can also play a role in determining an individual's threshold of hearing. Additionally, exposure to loud noises, such as in a noisy work environment, can cause temporary or permanent changes to the threshold of hearing.

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