build a simple narrowband acoustic reciever

[s4172718]

Hi everyone! For my electronics course, one of the requirements of the practical component, is to build a narrow band acoustic receiver to investigate the reliability of an underwater acoustic communications system. The narrowband audio receiver must:
- Be constructed out of discrete components
- Have a differential stage as the input stage
- Use feedback in an appropriate way in the design
We already have a circuit which measures the conductivity of water (using a water sample as a resistor) apparently, on the demo day, there will be a microphone which gives off water "sounds" which we use as the input to the reciever.
Any ideas?
Cheers,
Greg.

 

[MikeMl]

Do you have a frequency about which the narrow band is centered?

What does the conductivity of water have to do with using water for acoustic communication?

Any spec for the signal level out of the "microphone"?

 

[s4172718]

We're supposed to design an overall circuit that has a conductivity measuring capability, acoustic sensor capability, and temperature sensor capability. We're supposed to imagine our circuit is onboard an ROV controlled from a ship. the frequency is derived from researching the acoustic properties of water. However, I keep running into these complicated looking RF circuit diagrams, some of the concepts we havn't even covered yet. The input to the acoustic part is supposed to be a differential pair. The conductivity circuit already uses an oscillator to convert the d.c input from a battery to an ac signal.

 

[carbonzit]

We're supposed to design an overall circuit that has a conductivity measuring capability, acoustic sensor capability, and temperature sensor capability. We're supposed to imagine our circuit is onboard an ROV controlled from a ship. the frequency is derived from researching the acoustic properties of water. However, I keep running into these complicated looking RF circuit diagrams, some of the concepts we havn't even covered yet. The input to the acoustic part is supposed to be a differential pair. The conductivity circuit already uses an oscillator to convert the d.c input from a battery to an ac signal.

You've probably already figured this out, but it'll be a hell of a lot easier if you don't try to make one "circuit" do all of these functions. I didn't read anything in your description that gave this as a requirement. So you'll have three separate circuits for three different functions, the way it would be done in the real world (unless someone came up with a really damned clever, and probably problem-prone way of combining all 3!).

 

[Maikel]

The conductivity of water (Electrical)..that doesnt make sense, but the temperature and db of the mic sure sounds are changes in air presure, so underwater it should have a new definition, changes in water vibrations, more cave style acoustics I would think. Your application marine rover.. like dolphins would hear, sure, I would use sonar for frequencies. sounds are not electrical. Any receiver is one way RF telemetry is two way pinging with vibrations. Satellites and HAARP send out frequencies to scan the geosphere with over a billion watts, perhaps researching her would help identifying the correct acoustic sensor, then I have a nice link DL4YHF's Audio Spectrum Analyser spectrum lab, load the human filter 50 hz for yur mic input it will plot the frequencies graphically, here you will see the Freq and DB of your microphone imputs, human speech is 50Hz so I guess dolphins woul dhe higher round 190 hz as they are in essence squeeling. Waterproof an Ectet mic and put it underwater say in a pool, hook it up to spectrum with the human filter configuration file loaded. Thats a start. Temperature is easy. Conductivity measuring, what is the range of dophin hearing thats the maximum conductivity water could hold for sound vibrations, is there a difference in a pool to a bed of rock or sand at the bottom, Im sure the sand would absorb more than marble or rock.