# How Far Can a Parabolic Reflector Detect a Whisper?

• skinnyl
In summary: JackIn summary, Jack is asking for help with an Advanced Acoustics assignment. The assignment involves determining the distance at which a whispered conversation can be heard from a system using a large parabolic reflector and a collector tube. The minimum sound level needed to be heard by the ear, the efficiency of the reflector, and the intensity level of a whisper at a certain distance are important factors in solving this problem. Jack is seeking guidance on which methods to use and research for this assignment.
skinnyl
Hi there all !

i have been given a question for my Advanced Acoustics assignment as follows:

An MI6 agent uses a large parabolic reflector of aperture diameter 1.20meters to focus a sound into a tube of diameter 10mm at 20% acoustic efficiency which then goes to the ear.

how far away can a whispered conversation be heard from the system?

assuming the intersity level of a whisper is 20dB at 1.0m from the source, which maybe assumed to be a point source.

i have no idea where to start with this. I am not asking for it to be done for me but a shove in the right direction would be appreciated. what methods should i be looking to use or research?

Cheers a lot

Jack

skinnyl said:
Hi there all !

i have been given a question for my Advanced Acoustics assignment as follows:

An MI6 agent uses a large parabolic reflector of aperture diameter 1.20meters to focus a sound into a tube of diameter 10mm at 20% acoustic efficiency which then goes to the ear.

how far away can a whispered conversation be heard from the system?

assuming the intersity level of a whisper is 20dB at 1.0m from the source, which maybe assumed to be a point source.

i have no idea where to start with this. I am not asking for it to be done for me but a shove in the right direction would be appreciated. what methods should i be looking to use or research?

Cheers a lot

Jack

To start, you need to know the minimum sound level that can be heard by the ear. Then you need to use the efficiency information to figure out how much sound power has to be captured by the reflector to deliver the minimum needed to the collector tube. Then you need to figure out how far away the reflector can be from the source and still capture that much power. How does the intensity level vary with distance?

Hi, that great. helped a lot!

Cheers

## 1. What is a parabolic reflector?

A parabolic reflector is a curved surface that reflects light or sound waves to a single focal point. It is shaped like a parabola, which is a U-shaped curve.

## 2. How does a parabolic reflector work?

A parabolic reflector works by reflecting incoming waves in such a way that they all converge at a single focal point. This allows for a more focused and concentrated beam of light or sound.

## 3. What are some common uses for parabolic reflectors?

Parabolic reflectors are commonly used in telescopes, satellite dishes, and flashlights. They are also used in solar energy systems to concentrate sunlight onto a single point.

## 4. What are the advantages of using a parabolic reflector?

One advantage of using a parabolic reflector is its ability to focus light or sound waves to a single point, making it useful for long-distance communication and energy collection. It also has a relatively simple design and is cost-effective to produce.

## 5. Are there any limitations to using a parabolic reflector?

One limitation of parabolic reflectors is that they can only focus waves that are parallel to the axis of the parabola. This means they are not effective for omnidirectional signals. They also require precise alignment and can be affected by external factors such as wind or temperature changes.