# Reflection of sound wave in an open organ pipe

• vcsharp2003
In summary, the conversation discusses how standing waves form in an open organ pipe and the reasoning behind the formation of reflected waves at the open end. The individual in the conversation expresses surprise at the idea of sound waves reflecting at the open end and provides reasoning for their confusion. Ultimately, it is explained that the pressure at the open end of the pipe plays a role in creating the reflected wave, resulting in a disturbance in the opposite direction of the original wave.
vcsharp2003
Homework Statement
How and why does a sound wave get reflected from the open end of an organ pipe?
Relevant Equations
None
I know that standing waves form in an open organ pipe. Since, standing waves can only form from superposition of original wave and reflected wave, so there must be a reflected wave in an open organ pipe. But I fail to understand how sound wave can reflect at the open end of organ pipe.

Why does this surprise you? It will be easier to address your question if you give the reasoning.

Orodruin said:
Why does this surprise you? It will be easier to address your question if you give the reasoning.
My understanding is that the sound wave should travel through the open end since there is no barrier. The air particles in a sound wave are vibrating parallel to wave direction. At the open end, the air particles vibrating should cause the air particles just outside the pipe to also start oscillating resulting in a wave outside the tube. The open end cannot exert a force on the air particles just inside the pipe to cause a reflected wave unlike a closed end.

Consider this: At the open end, pressure is approximately constant. If there was just a wave towards the open end, there is no way that pressure could be maintained constant.

vcsharp2003
Orodruin said:
Consider this: At the open end, pressure is approximately constant. If there was just a wave towards the open end, there is no way that pressure could be maintained constant.
So, when pressure is low just inside the open end then air from outside would rush to inside the open end causing particles to move just inside the open end resulting in a wave traveling in opposite direction to original wave.

If pressure is high just inside the tube compared to outside then air would rush towards the outside that causes air particles to move just inside the open end resulting in a new wave/ disturbance inside the pipe in opposite direction to original wave.

## 1. How does a sound wave reflect in an open organ pipe?

When a sound wave enters an open organ pipe, it travels down the length of the pipe and reflects off the open end. This reflection causes the sound wave to reverse its direction and travel back towards the source.

## 2. What determines the frequency of the reflected sound wave in an open organ pipe?

The frequency of the reflected sound wave in an open organ pipe is determined by the length of the pipe and the speed of sound in the medium. Longer pipes produce lower frequencies, while shorter pipes produce higher frequencies.

## 3. How does the diameter of an open organ pipe affect the reflection of sound waves?

The diameter of an open organ pipe does not affect the reflection of sound waves. However, it does affect the resonance of the pipe, which can impact the overall sound produced by the pipe.

## 4. Can the reflection of sound waves in an open organ pipe be manipulated?

Yes, the reflection of sound waves in an open organ pipe can be manipulated by changing the length of the pipe. This can be done by opening or closing holes along the length of the pipe, which changes the effective length of the pipe and therefore the frequency of the reflected sound wave.

## 5. What is the difference between a closed and open organ pipe in terms of sound wave reflection?

In a closed organ pipe, the sound wave reflects off the closed end of the pipe, resulting in a node (point of no vibration) at that end. In an open organ pipe, the sound wave reflects off the open end of the pipe, resulting in an antinode (point of maximum vibration) at that end. This difference in reflection affects the harmonics and overall sound produced by the pipe.

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