If this is wrong group to ask about hydrophones, let me know what is better.

1) In all DIY projects hydrophones are made based on piezoelement. Why
piezo?
2) Normal (easy) way to do it is to sandwich piezo between two plexiglass
(3-4mm) discs and put o-ring inbetween.
- How thickness of plexiglass affects sound quality and performance?
- How air volume inside 'sandwich' affects sound quality and
performance?
3) What would be good link to find more info?

/timo

"TIMO PARRU" wrote in message ...
If this is wrong group to ask about hydrophones, let me know what is better.

1) In all DIY projects hydrophones are made based on piezoelement. Why
piezo?
2) Normal (easy) way to do it is to sandwich piezo between two plexiglass
(3-4mm) discs and put o-ring inbetween.
- How thickness of plexiglass affects sound quality and performance?
- How air volume inside 'sandwich' affects sound quality and
performance?
3) What would be good link to find more info?

/timo

alt.sci.physics.acoustics could be it for this question. I would think
that the choice of piezo for this purpose would be the higher wave
impedance of water. According to my table it is 1480000 Ns/m3,
compared to 415 Ns/m3 for air. The wave impedance tells how much
pressure that has to be used to acheive a certain particle velocity in
a plane wave (wave impedance=p/v). Obviously water needs more
pressure, and I guess piezo transducers are better suited to do this.
Electromagnetic transducers can provide large motion, but relatively
little force (pressure). This suits air better.
I am partly guessing here, does anyone have another opinion?

I don't have the answer to your other questions.

"TIMO PARRU" wrote in message ...
If this is wrong group to ask about hydrophones, let me know what is better.

1) In all DIY projects hydrophones are made based on piezoelement. Why
piezo?
2) Normal (easy) way to do it is to sandwich piezo between two plexiglass
(3-4mm) discs and put o-ring inbetween.
- How thickness of plexiglass affects sound quality and performance?
- How air volume inside 'sandwich' affects sound quality and
performance?
3) What would be good link to find more info?

/timo

alt.sci.physics.acoustics could be it for this question. I would think
that the choice of piezo for this purpose would be the higher wave
impedance of water. According to my table it is 1480000 Ns/m3,
compared to 415 Ns/m3 for air. The wave impedance tells how much
pressure that has to be used to acheive a certain particle velocity in
a plane wave (wave impedance=p/v). Obviously water needs more
pressure, and I guess piezo transducers are better suited to do this.
Electromagnetic transducers can provide large motion, but relatively
little force (pressure). This suits air better.
I am partly guessing here, does anyone have another opinion?

I don't have the answer to your other questions.

"TIMO PARRU" wrote in message ...
If this is wrong group to ask about hydrophones, let me know what is better.

1) In all DIY projects hydrophones are made based on piezoelement. Why
piezo?
2) Normal (easy) way to do it is to sandwich piezo between two plexiglass
(3-4mm) discs and put o-ring inbetween.
- How thickness of plexiglass affects sound quality and performance?
- How air volume inside 'sandwich' affects sound quality and
performance?
3) What would be good link to find more info?

/timo

alt.sci.physics.acoustics could be it for this question. I would think
that the choice of piezo for this purpose would be the higher wave
impedance of water. According to my table it is 1480000 Ns/m3,
compared to 415 Ns/m3 for air. The wave impedance tells how much
pressure that has to be used to acheive a certain particle velocity in
a plane wave (wave impedance=p/v). Obviously water needs more
pressure, and I guess piezo transducers are better suited to do this.
Electromagnetic transducers can provide large motion, but relatively
little force (pressure). This suits air better.
I am partly guessing here, does anyone have another opinion?

I don't have the answer to your other questions.

"TIMO PARRU" wrote in message ...
If this is wrong group to ask about hydrophones, let me know what is better.

1) In all DIY projects hydrophones are made based on piezoelement. Why
piezo?
2) Normal (easy) way to do it is to sandwich piezo between two plexiglass
(3-4mm) discs and put o-ring inbetween.
- How thickness of plexiglass affects sound quality and performance?
- How air volume inside 'sandwich' affects sound quality and
performance?
3) What would be good link to find more info?

/timo

alt.sci.physics.acoustics could be it for this question. I would think
that the choice of piezo for this purpose would be the higher wave
impedance of water. According to my table it is 1480000 Ns/m3,
compared to 415 Ns/m3 for air. The wave impedance tells how much
pressure that has to be used to acheive a certain particle velocity in
a plane wave (wave impedance=p/v). Obviously water needs more
pressure, and I guess piezo transducers are better suited to do this.
Electromagnetic transducers can provide large motion, but relatively
little force (pressure). This suits air better.
I am partly guessing here, does anyone have another opinion?

I don't have the answer to your other questions.

Svante wrote:

alt.sci.physics.acoustics could be it for this question. I would think
that the choice of piezo for this purpose would be the higher wave
impedance of water. According to my table it is 1480000 Ns/m3,
compared to 415 Ns/m3 for air. The wave impedance tells how much
pressure that has to be used to acheive a certain particle velocity in
a plane wave (wave impedance=p/v). Obviously water needs more
pressure, and I guess piezo transducers are better suited to do this.
Electromagnetic transducers can provide large motion, but relatively
little force (pressure). This suits air better.
I am partly guessing here, does anyone have another opinion?


Perhaps just to corroborate yours. Years ago I worked for a company that built underwater acoustic devices including pingers. I know that even a 15 watt pinger could be heard underwater nearly 20 miles away. I also know that you don't turn one on while testing if there are scuba divers in the water--they get very irate :-)

- Jeff

Svante wrote:

alt.sci.physics.acoustics could be it for this question. I would think
that the choice of piezo for this purpose would be the higher wave
impedance of water. According to my table it is 1480000 Ns/m3,
compared to 415 Ns/m3 for air. The wave impedance tells how much
pressure that has to be used to acheive a certain particle velocity in
a plane wave (wave impedance=p/v). Obviously water needs more
pressure, and I guess piezo transducers are better suited to do this.
Electromagnetic transducers can provide large motion, but relatively
little force (pressure). This suits air better.
I am partly guessing here, does anyone have another opinion?


Perhaps just to corroborate yours. Years ago I worked for a company that built underwater acoustic devices including pingers. I know that even a 15 watt pinger could be heard underwater nearly 20 miles away. I also know that you don't turn one on while testing if there are scuba divers in the water--they get very irate :-)

- Jeff

Svante wrote:

alt.sci.physics.acoustics could be it for this question. I would think
that the choice of piezo for this purpose would be the higher wave
impedance of water. According to my table it is 1480000 Ns/m3,
compared to 415 Ns/m3 for air. The wave impedance tells how much
pressure that has to be used to acheive a certain particle velocity in
a plane wave (wave impedance=p/v). Obviously water needs more
pressure, and I guess piezo transducers are better suited to do this.
Electromagnetic transducers can provide large motion, but relatively
little force (pressure). This suits air better.
I am partly guessing here, does anyone have another opinion?


Perhaps just to corroborate yours. Years ago I worked for a company that built underwater acoustic devices including pingers. I know that even a 15 watt pinger could be heard underwater nearly 20 miles away. I also know that you don't turn one on while testing if there are scuba divers in the water--they get very irate :-)

- Jeff

Svante wrote:

alt.sci.physics.acoustics could be it for this question. I would think
that the choice of piezo for this purpose would be the higher wave
impedance of water. According to my table it is 1480000 Ns/m3,
compared to 415 Ns/m3 for air. The wave impedance tells how much
pressure that has to be used to acheive a certain particle velocity in
a plane wave (wave impedance=p/v). Obviously water needs more
pressure, and I guess piezo transducers are better suited to do this.
Electromagnetic transducers can provide large motion, but relatively
little force (pressure). This suits air better.
I am partly guessing here, does anyone have another opinion?


Perhaps just to corroborate yours. Years ago I worked for a company that built underwater acoustic devices including pingers. I know that even a 15 watt pinger could be heard underwater nearly 20 miles away. I also know that you don't turn one on while testing if there are scuba divers in the water--they get very irate :-)

- Jeff

On Sat, 14 Feb 2004 07:33:52 GMT, "TIMO PARRU"
wrote:

If this is wrong group to ask about hydrophones, let me know what is better.

1) In all DIY projects hydrophones are made based on piezoelement. Why
piezo?

2) Normal (easy) way to do it is to sandwich piezo between two plexiglass
(3-4mm) discs and put o-ring inbetween.
- How thickness of plexiglass affects sound quality and performance?
- How air volume inside 'sandwich' affects sound quality and
performance?
3) What would be good link to find more info?

---
http://www.google.com/search?q=under...&start=10&sa=N

http://www.google.com/search?hl=en&i...e+construction


--
John Fields

On Sat, 14 Feb 2004 07:33:52 GMT, "TIMO PARRU"
wrote:

If this is wrong group to ask about hydrophones, let me know what is better.

1) In all DIY projects hydrophones are made based on piezoelement. Why
piezo?

2) Normal (easy) way to do it is to sandwich piezo between two plexiglass
(3-4mm) discs and put o-ring inbetween.
- How thickness of plexiglass affects sound quality and performance?
- How air volume inside 'sandwich' affects sound quality and
performance?
3) What would be good link to find more info?

---
http://www.google.com/search?q=under...&start=10&sa=N

http://www.google.com/search?hl=en&i...e+construction


--
John Fields

On Sat, 14 Feb 2004 07:33:52 GMT, "TIMO PARRU"
wrote:

If this is wrong group to ask about hydrophones, let me know what is better.

1) In all DIY projects hydrophones are made based on piezoelement. Why
piezo?

2) Normal (easy) way to do it is to sandwich piezo between two plexiglass
(3-4mm) discs and put o-ring inbetween.
- How thickness of plexiglass affects sound quality and performance?
- How air volume inside 'sandwich' affects sound quality and
performance?
3) What would be good link to find more info?

---
http://www.google.com/search?q=under...&start=10&sa=N

http://www.google.com/search?hl=en&i...e+construction


--
John Fields

On Sat, 14 Feb 2004 07:33:52 GMT, "TIMO PARRU"
wrote:

If this is wrong group to ask about hydrophones, let me know what is better.

1) In all DIY projects hydrophones are made based on piezoelement. Why
piezo?

2) Normal (easy) way to do it is to sandwich piezo between two plexiglass
(3-4mm) discs and put o-ring inbetween.
- How thickness of plexiglass affects sound quality and performance?
- How air volume inside 'sandwich' affects sound quality and
performance?
3) What would be good link to find more info?

---
http://www.google.com/search?q=under...&start=10&sa=N

http://www.google.com/search?hl=en&i...e+construction


--
John Fields