Solving Sound Reduction Index Problem: Air to Water

  • Thread starter tyco05
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    Acoustics
In summary, the conversation discusses the topic of acoustics and the difficulties faced by the speaker in understanding it. They ask for help in calculating the normal incidence sound reduction index for sound traveling from air to water, and eventually find the answer to be 29.9 dB using the formula R_n = 10log_{10}(\frac{1}{\tau}) with the values given for the speed and density of air and water.
  • #1
tyco05
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I hate acoustics, but unfortunately I have to get through this subject.
Most of the time I don't even know where to start with the problems, and this is one of those times.
I'm sure there's some easy formula for it, but I just can't seem to find it.

What is the normal incidence sound reduction index for sound traveling from air to water in dB? Assume that the speed of sound is 337m/s in air and 1470m/s in water. Assume that the density of air is 1.1kg/m^3 and that the density of water is 996 kg/m^3

Everything I try I get the wrong answer. Please can anyone give me a hint of how to start this question? It's got to be easy!
 
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  • #2
Can you calculate the transmission coefficient? Hint: Think acoustic impedance!

The sound reduction index (probably in your textbook) is SRI = -10 log T = 10 log 1/T
 
  • #3
Got it, thanks.

So I use

[tex]R_n = 10log_{10}(\frac{1}{\tau})[/tex]

Where

[tex]\tau=\frac{4c_1\rho_1c_2\rho_2}{(c_1\rho_1+c_2\rho_2)^2}[/tex]

and I ended up with 29.9 dB

cheers
 

1. What is the Sound Reduction Index (SRI) and why is it important in air to water sound transmission?

The Sound Reduction Index (SRI) is a measure of how much sound is reduced when it travels from one medium to another, in this case from air to water. It is important because it tells us how much sound will be transmitted between these two mediums, which is crucial in understanding and solving sound reduction problems.

2. How is the Sound Reduction Index (SRI) calculated?

The SRI is calculated by measuring the sound pressure levels on both sides of a partition separating the two mediums, and then using a formula to determine the difference in decibels. This difference is then converted into the SRI value, which ranges from 0-100.

3. What factors affect the Sound Reduction Index (SRI) in air to water sound transmission?

Several factors can affect the SRI in air to water sound transmission, including the thickness and material of the partition, the frequency of the sound being transmitted, and the angle at which the sound hits the partition. The temperature and salinity of the water can also have an impact on the SRI.

4. How can the Sound Reduction Index (SRI) problem be solved in air to water sound transmission?

To solve the SRI problem in air to water sound transmission, the most effective method is to use soundproofing materials such as barriers, absorbers, and diffusers. These materials can help reduce the amount of sound that is transmitted between the two mediums, thus improving the SRI.

5. Are there any regulations or standards for the Sound Reduction Index (SRI) in air to water sound transmission?

Yes, there are regulations and standards for the SRI in air to water sound transmission. In the United States, the American National Standards Institute (ANSI) has set standards for SRI testing and rating. Additionally, there may be local or industry-specific regulations that need to be followed in order to ensure proper sound reduction in air to water sound transmission.

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