[ Technical Discussions ]
[ Follow Ups ] [ Post Followup ] [ Help ]

---

Re: alternative generation of ultrasound waves

Posted by: Godfrey Hands (PID_83), E-mail: godfrey@ndt-consultants.co.uk, on December 20, 2004 at 09:42 :

In Reply to: alternative generation of ultrasound waves posted by : kostas papas , E-mail: lakourtis@hotmail.com, on December 17, 2004 at 23:43 :

----------- Start Original Message -----------
: The use of piezoelectric transducers is well spread for the generation and receive of ultrasound waves. The use of microphones is also an existing technique for receiving acoustic and ultrasonic waves.
: However what about microphone-speaker technology to generate and transmit ultrasound waves through solid material?
: Is mechanical coupling (efficiency coef) a problem when generating waves by means of speakers?
: This is an academic question that was brought about after using piezoelectric transducers.
------------ End Original Message ------------

Microphones tend to be limited in frequency to tens of KHz (up to about 40). This will efectively limit the frequency of ultrasound that you can generate and receive, which in turn will limit the detectability of smaller defects (conventionally it is accepted that 0.25 wavelength down to 0.1 wavelength is the detection limit).
There is an "Air Scan" system that operates with lower frequency ultrasound. This (I believe) has piezo transducers, but operates at a significantly reduced frequency (in the KHz region). There is also the acoustic mis-matching problem to overcome between Air and most solids that are being interrogated.

Other alternative generation methods for ultrasound (at "Normal" or elevated frequencies, i.e. 1 MHz to 20 MHz) are EMAT or Laser Generation.

Hope this helps your studies.

Godfrey Hands

---

Follow Ups:

• Re: alternative generation of ultrasound waves Wolfgang Bisle 14:12 Dec-20-2004 (1)
  • Re: alternative generation of ultrasound waves kostas papas 16:33 Dec-21-2004 (0)

---

Post a Followup:

Name:
E-Mail:
Subject:

Comments:
----------- Start Original Message ----------- : : The use of piezoelectric transducers is well spread for the generation and receive of ultrasound waves. The use of microphones is also an existing technique for receiving acoustic and ultrasonic waves. : : However what about microphone-speaker technology to generate and transmit ultrasound waves through solid material? : : Is mechanical coupling (efficiency coef) a problem when generating waves by means of speakers? : : This is an academic question that was brought about after using piezoelectric transducers. : Microphones tend to be limited in frequency to tens of KHz (up to about 40). This will efectively limit the frequency of ultrasound that you can generate and receive, which in turn will limit the detectability of smaller defects (conventionally it is accepted that 0.25 wavelength down to 0.1 wavelength is the detection limit). : There is an "Air Scan" system that operates with lower frequency ultrasound. This (I believe) has piezo transducers, but operates at a significantly reduced frequency (in the KHz region). There is also the acoustic mis-matching problem to overcome between Air and most solids that are being interrogated. : Other alternative generation methods for ultrasound (at "Normal" or elevated frequencies, i.e. 1 MHz to 20 MHz) are EMAT or Laser Generation. : Hope this helps your studies. : Godfrey Hands ------------ End Original Message ------------

Optional Link URL:	Example: "http://www....html". Alternative write "http://www.ndt.net/wshop/attach/filename.htm" if you transfered a filename.htm via FTP
Link Title: is important!	Information on my Home Page
Optional Image URL:	http://www....gif

Attention! Please click the button only once. This may take a moment to process

---

[ Technical Discussions ] [ All Message Boards ] [ Help ]