Previous in Forum: DIY USB Battery Power Pack   Next in Forum: Timer Control - 16F877 Microcontroller
Close
Close
Close
7 comments
Participant

Join Date: Jan 2009
Location: Trivandrum,India
Posts: 3

The Best Ultrasound Project

02/03/2009 9:26 AM

yeah, here i am..

with more details about my project.. as i said i am doing a project, we named as ultra sound.. try to make sound unidirectional..

we have two options

1) here we are mixing a sound of 1 khz with an ultrasonic wave of 40 khz to give out frequencies of 41 khz and 39 khz and we are using two ultrasonic transducers to emit these frequencies, and by using the beating phenomenon, we hope we can generate an audible frequency of 2 hz that is to be unidirectinal... and as we are suppossed to reproduce that 1 khz frequency signal we may use a frequency divider of factor 2 to divide that 1 khz signal giving .5hz.. and we can do the same process of mixing ... and get a beating frequency 1khz(f1-f2=40.5-39.5)

2) or else.. we may use another technique

i observed the beating sigals generated in the air have a similar pattern that of a DSB (double side band-suppressed carrier) modulated signal, so i think we can modulate these signals(39.5and 40.5) to give out a dsb signal of frequency components (f1-f2=1khz, and f1=f2=80khz).. and can use an ultrasonic transducer to emit tis signal and as the second frequency componet is of ultrasonic range we may not here it and i think the first frequency component(f1-f2 khz) can stimulate our ear, and this signal should be unidirectional.............

i await your opinion

__________________
....Sankar....
Register to Reply
Pathfinder Tags: ultrasound
User-tagged by 1 user
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Guru
Hobbies - HAM Radio - New Member Hobbies - Model Rocketry - New Member

Join Date: Jan 2007
Posts: 792
Good Answers: 51
#1

Re: The Best Ultrasound Project

02/03/2009 10:03 AM

Have you seen the interviews with Joe Pompei, and one with Woody Norris on CR4.

From what I gather you are saying they both have companies based on what you are trying to do, so reading the details on their websites may help you.

Register to Reply
Guru
Hobbies - HAM Radio - New Member

Join Date: Oct 2006
Location: Vancouver (not BC) Washington (not DC) US of A
Posts: 1261
Good Answers: 12
#2

Re: The Best Ultrasound Project

02/03/2009 10:45 AM

I have some ideas which might help, (now that I know what we are talking about), but I need to draw some pictures first (like a cute analog multiplier). I will get back to you.

Bill

Register to Reply
Guru
Hobbies - HAM Radio - New Member

Join Date: Oct 2006
Location: Vancouver (not BC) Washington (not DC) US of A
Posts: 1261
Good Answers: 12
#7
In reply to #2

Re: The Best Ultrasound Project

02/05/2009 12:09 PM

Back at the ranch,

Below is the multiplier...

When the analog gate is off, the circuit has a gain of +1. When the gate is on, the gain is -1. This results in a DSB suppressed carrier modulator. Only problem is that both sidebands are on the same output. With only two KHz spacing between them, it would be difficult to use filtering to seperate the two.

If you look at the "phase" method of single sideband modulation you will find that the output stage is a "summer". If you take the sum of the two input signals you get one sideband. If you take the difference of the two signals, you get the other sideband. So if you build 2 summers, in parallel, you can get both sidebands at the same time.

If all you are interested in is synchronous multiples of a 1 KHz signal, I would look at a phase locked loop. Run the local oscillator at 4 KHz, divide it by 4 to run the phase comparator. This would give you 4 KHz, 2 KHz, and 1 KHz synchronous with the incoming signal

Another thought is that if you are competent in DSP, run your input signals through an A/D converter, you can do all the work in a micro-controller, and change the software as needed. If method "A" doesn't work, change software to method "B".

Enough for now.

Bill

Register to Reply
Guru

Join Date: Dec 2006
Location: Germany 49° 26' N, 7° 46' O
Posts: 1950
Good Answers: 109
#3

Re: The Best Ultrasound Project

02/04/2009 4:53 AM

Hi,

first approach is nonlinear mixing thus generating sum and difference frequencies.

Second approach is linear superposition of two nearby frequencies.

Where is the nonlinear mechnism that translates the two high frequencies back to audible?

RHABE

Register to Reply
Anonymous Poster
#6
In reply to #3

Re: The Best Ultrasound Project

02/04/2009 10:04 PM

i think air itself is non linear and act as the translation mechanism.. okay.

Register to Reply
Guru

Join Date: Aug 2005
Location: Hemel Hempstead, UK
Posts: 5265
Good Answers: 287
#4

Re: The Best Ultrasound Project

02/04/2009 6:18 AM

Lots to trawl through, but, lots of interesting stuff here:-

http://cr4.globalspec.com/blogentry/4643/Beat-Frequencies-Newsletter-Challenge-01-22-08

__________________
We are alone in the universe, or, we are not. Either way it's incredible... Adapted from R. Buckminster Fuller/Arthur C. Clarke
Register to Reply
Guru
Engineering Fields - Control Engineering - New Member China - Member - New Member

Join Date: Sep 2006
Location: CHINA
Posts: 2946
Good Answers: 14
#5

Re: The Best Ultrasound Project

02/04/2009 7:50 AM

haha, beat frequency.

1# point out Pompei may help you with it.

Register to Reply
Register to Reply 7 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Copy to Clipboard

Users who posted comments:

Anonymous Poster (1); cnpower (1); frankd20 (1); Randall (1); RHABE (1); Sciesis2 (2)

Previous in Forum: DIY USB Battery Power Pack   Next in Forum: Timer Control - 16F877 Microcontroller

Advertisement