amcneilly wrote:> Thanks for your help. I have successfully detected my 20 khz tone > using Goertzel algorithm using Matlab. > > What i would like to do now is change the sender signal and the > detection algorithm to help reduce the problem of detection of > background sound. The goal is to detect from a microphone a signal > from a transmitter with minimal interference from background sound. i > can tolerate a low percentage of false positives. > > What i was thinking is mixing a 20 khz tone and 19 khz . i am a novice > to DSP. What approach would you guys recommend?If I had control of the transmitter and receiver in real time, I would use a synchronous detector. For practical purposes, extraneous noise just disappears.>> Would a monochromatic tone a specific frequency be a pure sin wave?Yes. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
detect tone
Started by ●July 28, 2009
Reply by ●August 1, 20092009-08-01
Reply by ●August 3, 20092009-08-03
On Jul 28, 5:09�am, amcneilly <amcnei...@gmail.com> wrote:> i have a computer microphone and i want to be able to detect a tone at > a specific frequency from the recording from the microphone. i want > the program to work with background sound. What methods are available ?Look up lock-in amplifier. Maurice Givens
Reply by ●August 3, 20092009-08-03
maury001@core.com wrote:> On Jul 28, 5:09 am, amcneilly <amcnei...@gmail.com> wrote: >> i have a computer microphone and i want to be able to detect a tone at >> a specific frequency from the recording from the microphone. i want >> the program to work with background sound. What methods are available ? > > Look up lock-in amplifier.I like the idea, but I think of a lock-in amplifier as an expensice instrument, while an adequate synchronous detector is pretty easily implemented in any of several ways. Whatever, it's the most straightforward way. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●August 4, 20092009-08-04
On 3 Aug., 23:42, Jerry Avins <j...@ieee.org> wrote:> maury...@core.com wrote: > > On Jul 28, 5:09 am, amcneilly <amcnei...@gmail.com> wrote: > >> i have a computer microphone and i want to be able to detect a tone at > >> a specific frequency from the recording from the microphone. i want > >> the program to work with background sound. What methods are available ? > > > Look up lock-in amplifier. > > I like the idea, but I think of a lock-in amplifier as an expensice > instrument, while an adequate synchronous detector is pretty easily > implemented in any of several ways.A lock-in amplifier is a special cas of a synchronous detector. You can buy it as expensive equipment, but it is also easily implemented on the PC with a sound card.
Reply by ●August 4, 20092009-08-04
On Aug 4, 9:31�am, Andor <andor.bari...@gmail.com> wrote:> On 3 Aug., 23:42, Jerry Avins <j...@ieee.org> wrote: > > > maury...@core.com wrote: > > > On Jul 28, 5:09 am,amcneilly<amcnei...@gmail.com> wrote: > > >> i have a computer microphone and i want to be able to detect a tone at > > >> a specific frequency from the recording from the microphone. i want > > >> the program to work with background sound. What methods are available ? > > > > Look up lock-in amplifier. > > > I like the idea, but I think of a lock-in amplifier as an expensice > > instrument, while an adequate synchronous detector is pretty easily > > implemented in any of several ways. > > A lock-in amplifier is a special cas of a synchronous detector. You > can buy it as expensive equipment, but it is also easily implemented > on the PC with a sound card.Whats a good tone detection method if the duration of my tone is 11 samples @ 44100 sample rate or 2.494331065760e-04 Seconds
Reply by ●August 4, 20092009-08-04
Andor wrote:> On 3 Aug., 23:42, Jerry Avins <j...@ieee.org> wrote: >> maury...@core.com wrote: >>> On Jul 28, 5:09 am, amcneilly <amcnei...@gmail.com> wrote: >>>> i have a computer microphone and i want to be able to detect a tone at >>>> a specific frequency from the recording from the microphone. i want >>>> the program to work with background sound. What methods are available ? >>> Look up lock-in amplifier. >> I like the idea, but I think of a lock-in amplifier as an expensice >> instrument, while an adequate synchronous detector is pretty easily >> implemented in any of several ways. > > A lock-in amplifier is a special cas of a synchronous detector. You > can buy it as expensive equipment, but it is also easily implemented > on the PC with a sound card.You can implement the functionality of lots of devices on a PC with a good sound card if you understand how they function. To design a simulated or hardware lock-in amplifier, one needs to understand synchronous detectors. Why go beyond that? Ebjoy your vacation. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●August 4, 20092009-08-04
amcneilly wrote:> On Aug 4, 9:31 am, Andor <andor.bari...@gmail.com> wrote: >> On 3 Aug., 23:42, Jerry Avins <j...@ieee.org> wrote: >> >>> maury...@core.com wrote: >>>> On Jul 28, 5:09 am,amcneilly<amcnei...@gmail.com> wrote: >>>>> i have a computer microphone and i want to be able to detect a tone at >>>>> a specific frequency from the recording from the microphone. i want >>>>> the program to work with background sound. What methods are available ? >>>> Look up lock-in amplifier. >>> I like the idea, but I think of a lock-in amplifier as an expensice >>> instrument, while an adequate synchronous detector is pretty easily >>> implemented in any of several ways. >> A lock-in amplifier is a special cas of a synchronous detector. You >> can buy it as expensive equipment, but it is also easily implemented >> on the PC with a sound card. > > Whats a good tone detection method if the duration of my tone is 11 > samples @ 44100 sample rate or 2.494331065760e-04 SecondsThere aren't any really good ones. The narrower a filter, the more time it takes to respond. A quarter of a millisecond is too short a time for "tone" to have meaning. Listen to the tine 'ticks' on WWV. They actually consist of five cycles of a sine wave (1 KHz?). Would you guess? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●August 4, 20092009-08-04
amcneilly wrote:> Whats a good tone detection method if the duration of my tone is 11 > samples @ 44100 sample rate or 2.494331065760e-04 SecondsAs usual: do-it-yourself method or hire-somebody-else method. VLV
Reply by ●August 4, 20092009-08-04
On Aug 4, 4:12=A0pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote:> amcneillywrote: > > Whats a good tone detection method if the duration of my tone is 11 > > samples @ 44100 sample rate or 2.494331065760e-04 Seconds > > As usual: do-it-yourself method or hire-somebody-else method. > > VLVThey reaction time is not critical. i can do an event based on the tone detection a few seconds after the event.THe problem is i need a good method to detect a very short 20khz signal 2.494331065760e-04
Reply by ●August 4, 20092009-08-04
amcneilly wrote:> On Aug 4, 4:12 pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote: > >>amcneillywrote: >> >>>Whats a good tone detection method if the duration of my tone is 11 >>>samples @ 44100 sample rate or 2.494331065760e-04 Seconds >> >>As usual: do-it-yourself method or hire-somebody-else method. >> > > They reaction time is not critical. i can do an event based on the > tone detection a few seconds after the event.THe problem is i need a > good method to detect a very short 20khz signal 2.494331065760e-04Let's see what can be done. This is going to be the business; my contact at the web site; please be particular in the description of the problem. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
