More Power Please!

[Ron]

I need a powerful 13 kHz acoustical transducer for a project, but the
current crop of piezo benders don't quite fitt the bill. There seems
to be dozens and dozens of designs for underwater transducers but
almost none for air transducers, so I started to wonder if anyone knew
if there were any simple ways to make acoustical lenses for the low
ultrasonic range?

Ron

[Salmon Egg]

In article

Post by Ron
I need a powerful 13 kHz acoustical transducer for a project, but the
current crop of piezo benders don't quite fitt the bill. There seems
to be dozens and dozens of designs for underwater transducers but
almost none for air transducers, so I started to wonder if anyone knew
if there were any simple ways to make acoustical lenses for the low
ultrasonic range?
Ron

In the film "The Graduate," the keyword was PLASTICS. In your case, the
key phrase is (acoustic) IMPEDANCE MATCHING. :-)

Bill

[Screwing With Ultrasound]

Post by Ron
I need a powerful 13 kHz acoustical transducer for a project,

Let me guess.....an ultrasonic screwdriver.

Post by Ron
but the current crop of piezo benders don't quite fitt the bill.

As you have already been told repeatedly.

Post by Ron
There seems to be dozens and dozens of designs for underwater transducers
but almost none for air transducers, so I started to wonder if anyone
knew if there were any simple ways to make acoustical lenses for the low
ultrasonic range?
Ron

Making an acoustic lens is easy, but the first step is finding a suitable
transducer. If you really mean powerful (which I doubt) I recommend
looking around for a crappy efficient, high-power dynamic tweeter that has
a strong 20dB+ undamped resonance at 13kHz. The problem is that the
tweeter is going to be large and you are not going to be able to power it
for very long from a 9-volt transistor radio battery.

[Ron]

Post by Screwing With Ultrasound
Making an acoustic lens is easy, but the first step is finding a suitable
transducer.  

Oh, really? How?

Ron


________
In the beginning was the rhythm, but I had forgotten and I was waiting
for the word."

-- Ray Manzarek --

[Peter Larsen]

Post by Ron
I need a powerful 13 kHz acoustical transducer for a project, but the
current crop of piezo benders don't quite fitt the bill. There seems
to be dozens and dozens of designs for underwater transducers but
almost none for air transducers, so I started to wonder if anyone knew
if there were any simple ways to make acoustical lenses for the low
ultrasonic range?

It is amazing that you find it difficult to find high acoustic output air
transducers.

Acoustic lenses are generally used to de-focus and disperse rather than to
focus.

It would appear that what you need is a JBL 075 or perhaps a Vitavox tweeter
or a clone thereof.

Be warned however that such units can cause instant severe permanent
acoustic trauma leading to lifelong tinnitus and that high frequency sounds
tend not to be sensed at their actual loudness.

Post by Ron
Ron

Kind regards

Peter Larsen

[Ron]

Post by Peter Larsen

Post by Ron
I need a powerful 13 kHz acoustical transducer for a project, but the
current crop of piezo benders don't quite fitt the bill. There seems
to be dozens and dozens of designs for underwater transducers but
almost none for air transducers, so I started to wonder if anyone knew
if there were any simple ways to make acoustical lenses for the low
ultrasonic range?

It is amazing that you find it difficult to find high acoustic output air
transducers.

Not so amazing when you consider most ultrasonic work is done either
in liquids or transmitted through solids by way of horns. Most
applications for air transducers are usually low power things like TV
controls and motion sensing, but when there is a need for high power,
people go with sirens and whistles-- very little call for any kind of
piezo transducers. Pity...

Ron

[Answerman]

Post by Ron

Post by Peter Larsen

Post by Ron
I need a powerful 13 kHz acoustical transducer for a project, but
the current crop of piezo benders don't quite fitt the bill. There
seems to be dozens and dozens of designs for underwater transducers
but almost none for air transducers, so I started to wonder if
anyone knew if there were any simple ways to make acoustical lenses
for the low ultrasonic range?

It is amazing that you find it difficult to find high acoustic output
air transducers.

Not so amazing when you consider most ultrasonic work is done either
in liquids or transmitted through solids by way of horns. Most
applications for air transducers are usually low power things like TV
controls and motion sensing, but when there is a need for high power,
people go with sirens and whistles-- very little call for any kind of
piezo transducers. Pity...
Ron

What you have said simply isn't true. There is considerable worldwide
interest in high-power air ultrasonic transducers for non-destructive
testing of materials that, for a variety of reasons, can not be placed in
water.

http://www.qmi-inc.com/airscan.html
http://www.airstar1.com/

There are 20kHz high-power air ultrasonic transducers. One of the
highest, if not the highest, output 20kHz air transucer is made by
Airmar.

http://www.airmartechnology.com/2009/air/ultrasonic-search-results.asp

However, in order to obtain high acoustic output and acceptable beamwidth
it is large. It is also very expensive.

At 20kHz, you are not going to either find or be able to build a piezo
transducer of reasonable size that holds a candle to a high power dynamic
tweetwer that is coupled to the air via a horn, especially if the tweeter
is a crappy tweeter and has a 10-20dB diaphragm resonance around 20kHz.
The problem is that you aren't going to be able to power it for more than
a few seconds using a 9-volt transistor radio battery for your inane
ultrasonic screwdriver applicaation. What you require is both high
output power and ultra-high efficiency, which simply doesn't exist at the
present time.

[Ron]

What you have said simply isn't true.  There is considerable worldwide
interest in high-power air ultrasonic transducers for non-destructive
testing of materials that, for a variety of reasons, can not be placed in
water.

I don't give a fig about NDT but I do know a few things about the
subject. One, is that resolution depends upon frequency-- which is
why megaHertz frequencies are preferable, and 2) sound that high
doesn't travel very far in air; maybe an inch or two at best before
losses become too great.
Since ya can't get great resolution at lower frequencies, airborne
testing is (and probably *always* will be) a novelty act, So my
comment stands: most interest in ultrasound is either liquid or
contact with solids, and very little use of air transducers. If you
fix that resolution problem, then *maybe* acoustical NDT will be a
bigh thing. Maybe...

At 20kHz, you are not going to either find or be able to build a piezo
transducer of reasonable size that holds a candle to a high power dynamic
tweetwer that is coupled to the air via a horn, especially if the tweeter  
is a crappy tweeter and has a 10-20dB diaphragm resonance around 20kHz.

'

Sigh...

With the proper choice of ceramic and enough drive voltage, I got 143
dB at 13 kHz from a piezo bender. Pretty good, yeah? Before stating
absolutes like that, you reallly should become sure of your facts.

The problem is that you aren't going to be able to power it for more than
a few seconds using a 9-volt transistor radio battery for your inane
ultrasonic screwdriver applicaation.

It's only "inane" because I did something you either didn't have the
intelligence to do, the imagination to do, or both. You are like all
the other jealous dicks who stand around pissing on the achievement of
others because you couldn't do something creative yourself. Douche...

Ron

[Answerman]

Post by Ron

What you have said simply isn't true.  There is considerable
worldwide interest in high-power air ultrasonic transducers for
non-destructive testing of materials that, for a variety of reasons,
can not be placed in water.

I don't give a fig about NDT but I do know a few things about the
subject. One, is that resolution depends upon frequency--

No it doesn't. Resolution depends upon wavelength. Consequently, the
resolution at 1MHz in water is about the same as the resolution at 200kHz
in air.

Post by Ron
which is
why megaHertz frequencies are preferable, and 2) sound that high
doesn't travel very far in air; maybe an inch or two at best before
losses become too great.

The problem is not the losses in air. The problems are 1) the inability to
get energy into a material under test because of the impedance mismatch
between air and the materil, and 2) the attenuation of sound in the
material itself.

Post by Ron
Since ya can't get great resolution at lower frequencies, airborne
testing is (and probably *always* will be) a novelty act, So my
comment stands: most interest in ultrasound is either liquid or
contact with solids, and very little use of air transducers. If you
fix that resolution problem, then *maybe* acoustical NDT will be a
bigh thing. Maybe...

At the present time air-coupled ultrasound is one of the primary NDT
methods that are used worldwide for assessing the integrity of bonds in
wood composite materials.

Post by Ron

At 20kHz, you are not going to either find or be able to build a
piezo transducer of reasonable size that holds a candle to a high
power dynamic tweetwer that is coupled to the air via a horn,
especially if the tweeter

 

is a crappy tweeter and has a 10-20dB diaphragm resonance around 20kHz.

'
Sigh...
With the proper choice of ceramic and enough drive voltage, I got 143
dB at 13 kHz from a piezo bender.

Not at any distance more than a few millimeters. Either that or the
equipment that you used to measure the SPL was unsuitable (eg a Radio Shack
SLM), malfunctioning, or was being used improperly.

Post by Ron
Pretty good, yeah? Before stating
absolutes like that, you reallly should become sure of your facts.

I am sure of my facts, which is why you have been searching for nearly a
decade for a "better" transducer. It's also why you will contine to be
unsuccessful.

Post by Ron

The problem is that you aren't going to be able to power it for more
than a few seconds using a 9-volt transistor radio battery for your
inane ultrasonic screwdriver applicaation.

It's only "inane" because I did something you either didn't have the
intelligence to do, the imagination to do, or both.

Before you ignorantly pontificate about my lack of intelligence and
imagination, how about providing a list of your acoustic patents. After
you provide a list of yours, I'll provide a list of mine, and we'll see
which of us lacks intelligence and imagination.

Post by Ron
You are like all
the other jealous dicks who stand around pissing on the achievement of
others because you couldn't do something creative yourself. Douche...

.Go wash your foul mouth out with soap.

[Ron]

Post by Answerman
Before you ignorantly pontificate about my lack of intelligence and
imagination, how about providing a list of your acoustic patents.  After
you provide a list of yours, I'll provide a list of mine, and we'll see
which of us lacks intelligence and imagination.

Whatever, monkey boy; whatever...

Ron

[Ron]

Post by Ron

Post by Answerman
Before you ignorantly pontificate about my lack of intelligence and
imagination, how about providing a list of your acoustic patents.  After
you provide a list of yours, I'll provide a list of mine, and we'll see
which of us lacks intelligence and imagination.

Whatever, monkey boy; whatever...
Ron

I may have done it first, but there are other people who also don't
think a working sonic screwdriver as being "inane:"


http://www.geek.com/articles/geek-cetera/uk-scientists-working-to-make-doctor-whos-sonic-screwdriver-real-20101210/

if the world's technical advancement depended upon the limited
imagination of most people, we would all be living in the dark with
candle-making being the ultimate science.

Ron