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The bellow of a territorial bull hippopotamus has been measured at 115 dB above the threshold of hearing. What is the sound intensity?

Short Answer

Expert verified
The sound intensity is approximately 0.316 W/m².

Step by step solution

01

Understanding the Decibel Formula

The sound intensity level in decibels (dB) is given by the formula: \[ L = 10 \log_{10}\left(\frac{I}{I_0}\right) \]where \(L\) is the sound level in dB, \(I\) is the sound intensity, and \(I_0\) is the reference intensity, commonly \(1 \times 10^{-12} \text{W/m}^2\), which represents the threshold of hearing.
02

Rearranging the Formula for Intensity

To find \(I\), the sound intensity, rearrange the formula:\[ 10 \log_{10}\left(\frac{I}{I_0}\right) = L \]Divide both sides by 10:\[ \log_{10}\left(\frac{I}{I_0}\right) = \frac{L}{10} \] Now, we need to solve for \(I\).
03

Solving for Sound Intensity \(I\)

To isolate \(I\), use the property of logarithms:\[ \frac{I}{I_0} = 10^{\frac{L}{10}} \] Multiply both sides by \(I_0\):\[ I = I_0 \times 10^{\frac{L}{10}} \] This expression allows us to calculate \(I\) based on the sound level \(L\).
04

Substituting Known Values

Substitute \(L = 115\,\text{dB}\) and \(I_0 = 1 \times 10^{-12} \, \text{W/m}^2\) into the formula:\[ I = 1 \times 10^{-12} \times 10^{\frac{115}{10}} \] Simplify the expression:\[ I = 1 \times 10^{-12} \times 10^{11.5} \]
05

Calculating the Intensity

Calculate \(10^{11.5}\) which is approximately \(3.16 \times 10^{11}\):\[ I = 1 \times 10^{-12} \times 3.16 \times 10^{11} = 3.16 \times 10^{-1} \, \text{W/m}^2 \] This is the sound intensity of the hippopotamus bellow.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Decibel Formula
The decibel formula is a mathematical representation to measure the intensity level of sound. It uses a logarithmic scale to describe the ratio of a particular sound intensity (\(I\)) to a reference intensity (\(I_0\)). The formula is expressed as: \[L = 10 \log_{10}\left(\frac{I}{I_0}\right)\]where - \(L\) is the sound level in decibels (dB),- \(I\) is the sound intensity,- \(I_0\) is the threshold of hearing, typically valued at \(1 \times 10^{-12} \text{W/m}^2\).This formula helps in converting the physical intensity of sound into a more comprehensible scale by using logarithms. The decibel scale is widely used due to its ability to manage a vast range of intensities without having to handle very large or very small numbers.
Sound Intensity Level
Sound intensity level is an expression of the power per unit area carried by a sound wave. It is a key factor when using the decibel scale to describe how loud a sound is. The concept is important because it provides a standardized way to compare different sounds based on how they are perceived by the average human ear.Sound intensity level is noted in decibels, often abbreviated as - dB. The intensity itself is the actual physical energy or power of the sound wave, typically measured in watts per square meter (\(W/m^2\)). The sound intensity level translates that into decibels using the previously discussed decibel formula, making it easier to assess and compare. Understanding this idea can assist in tackling problems related to sound physics effectively.
Logarithmic Scale
A logarithmic scale is a scale of measurement that uses the logarithm of a physical quantity instead of the quantity itself. When dealing with sound intensity, a logarithmic scale is particularly useful.
  • It compresses a wide range of values into a more manageable scale.
  • Helps represent exponential changes in magnitude visually.
  • It is expressed in powers of ten, making rapid changes easier to interpret.
In sound measurement, the logarithmic scale helps us move from physical measurements to perceived loudness. This is crucial because the human ear perceives sound intensity on a logarithmic scale naturally, a phenomenon that aligns well with how our hearing system evolved to manage different sound levels.
Hearing Threshold
The hearing threshold represents the minimum sound level that the average human ear can detect. This is a crucial baseline in sound intensity calculations.
  • The standard reference sound intensity level is \(I_0 = 1 \times 10^{-12} \text{W/m}^2\).
  • This small value indicates that even extremely faint sounds can be detected by the human ear.
When calculating the sound intensity level in decibels using the decibel formula, this threshold works as a benchmark for the expression. The importance of the hearing threshold cannot be understated as it allows us to understand how subtle changes in sound intensity are perceived relative to the quietest sound detectable by the human ear.

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Most popular questions from this chapter

A man stands at the midpoint between two speakers that are broadcasting an amplified static hiss uniformly in all directions. The speakers are 30.0 m apart and the total power of the sound coming from each speaker is 0.500 W. Find the total sound intensity that the man hears (a) when he is at his initial position halfway between the speakers, and (b) after he has walked 4.0 m directly toward one of the speakers.

Two wires are parallel, and one is directly above the other. Each has a length of 50.0 m and a mass per unit length of 0.020 kg/m. However, the tension in wire \(A\) is \(6.00 \times 10^{2} \mathrm{N},\) and the tension in wire \(\mathrm{B}\) is \(3.00 \times 10^{2} \mathrm{N}\) . Transverse wave pulses are generated simultaneously, one at the left end of wire A and one at the right end of wire B. The pulses travel toward each other. How much time does it take until the pulses pass each other?

When Gloria wears her hearing aid, the sound intensity level increases by 30.0 dB. By what factor does the sound intensity increase?

The volume control on a surround-sound amplifier is adjusted so the sound intensity level at the listening position increases from 23 to 61 dB. What is the ratio of the final sound intensity to the original sound intensity?

From a vantage point very close to the track at a stock car race, you hear the sound emitted by a moving car. You detect a frequency that is 0.86 times as small as the frequency emitted by the car when it is stationary. The speed of sound is 343 m/s. What is the speed of the car?

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