User:Pranav Rathi/Notebook/OT/2011/10/11/Device for studying acoustic and mechanical noise in optical setups: Difference between revisions
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==Construction== | ==Construction== | ||
Construction of AMNR is easy just solder the condenser mic on the one end and lead on the other end. Snug the mic into the ear-plug of the stethoscope and tape it as shown in the slide 2. To activate the mic just put the lead into the mic jack of the sound card. | Construction of AMNR is easy just solder the condenser mic on the one end and lead on the other end. Snug the mic into the ear-plug of the stethoscope and tape it as shown in the slide 2. To activate the mic just put the lead into the mic jack of the sound card. | ||
Noise Investigator and Helper helps with reading and identification of the noise frequencies; slide 3&4. This program takes the signal from mic and plot it on the wave form graph than it does FFT to distinguish the different frequencies in the signal with their relative power in DB. This program can also write and read the data for future use. Helper part of the program can helps in many ways; it can help with deciding which material is better for certain frequency range, it can help with deciding which setup is better and it can also help with choosing that which part on optical table has less mechanical noise. It does it by feeding the power values of particular frequency from FFT power spectrum graph into an array and then taking a mean and feeding it into an another array (you can choose your desired name for that value and feed it). Than the whole process is repeated again for different frequencies and compare the values in the last. | Noise Investigator and Helper helps with reading and identification of the noise frequencies; slide 3&4. This program takes the signal from mic and plot it on the wave form graph than it does FFT to distinguish the different frequencies in the signal with their relative power in DB. This program can also write and read the data for future use. Helper part of the program can helps in many ways; it can help with deciding which material is better for certain frequency range, it can help with deciding which setup is better and it can also help with choosing that which part on optical table has less mechanical noise. It does it by feeding the power values of particular frequency from FFT power spectrum graph into an array and then taking a mean and feeding it into an another array (you can choose your desired name for that value and feed it). Than the whole process is repeated again for different frequencies and compare the values in the last. | ||
Tone generator is another program of this setup; slide 5. It can generate a tone of any frequency, but it does not matter because every electronics and output device (speaker) have its own frequency response range, so only the frequencies in that range will workout. This program is helpful with testing of frequency response of different materials and setups. Now for example I can generate a range of frequencies to test the mechanical frequency response of the optical table at certain distance or place on the table. Same can be done with microscope or other stages or breadboards or different isolation materials/setups by reading the generated signal through AMNR. | Tone generator is another program of this setup; slide 5. It can generate a tone of any frequency, but it does not matter because every electronics and output device (speaker) have its own frequency response range, so only the frequencies in that range will workout. This program is helpful with testing of frequency response of different materials and setups. Now for example I can generate a range of frequencies to test the mechanical frequency response of the optical table at certain distance or place on the table. Same can be done with microscope or other stages or breadboards or different isolation materials/setups by reading the generated signal through AMNR. | ||
Revision as of 15:07, 20 October 2011
Introduction
All optical setups are subjected to the mechanical and airborne acoustic noise generated by various electronic and mechanical devices such as computers and air-vents in a lab. Optical setups such as optical tweezers are very sensitive to these noises. Optical tweezers like ours is so sensitive that it almost woke like a microphone. Currently it is reading all kinds of mechanical and airborne noises which are very troublesome for DNA unzipping and overstretching experiments. So I had to do a full scale investigation of these noises[[1]]. To do it I had to create this device: I named it Acoustic & Mechanical Noise Reader (AMNR). This device is nothing but a condenser microphone inside the ear-plug of a stethoscope. But it is so sensitive that it can read the mechanical noise up to -95DB (believe it or not), and it just uses a regular computer sound card with a Lab View V9 program. This whole setup has three parts; AMNR, noise investigator and helper program and, tone generator and speaker.
The whole purpose of this device is following:
- Identify the airborne noise frequencies around the tweezers and their source.
- Identify the mechanical noise (vibrations) frequencies in the optical table and their source.
- Help me chose and design the right setup (stages and sample holders) on the microscope.
- Help me in designing and searching ways to isolate the optical trap form acoustic and mechanical noise.
Most of this I discussed in the “Noise issue with the optical tweezers’’ page of my note book[[2]]. In this page I will just discuss the construction and demonstration briefly.
Hardware
The hardware is pretty simple:
- Classic ll S.E. stethoscope by 3M Littmann. This is one of the best in the market used by cardiologists, with nominal price.
- Condenser microphone. Omnidirectional mic with frequency response 50Hz to 1.5kHz.
- 3.5mm headphone lead.
- Investigator and helper Lab View V9. Link to download: [3].
- Tone generator Lab View V9. Link to download:[4].
- 5.25" speaker by Virtual Reality Sounds Labs. The speaker has frequency response from 100Hz to 20kHz, which is more than enough for me.
I do not know any specifications of the sound-card and external amplifier i am using to generate the tone of different frequencies.
Construction
Construction of AMNR is easy just solder the condenser mic on the one end and lead on the other end. Snug the mic into the ear-plug of the stethoscope and tape it as shown in the slide 2. To activate the mic just put the lead into the mic jack of the sound card.
Noise Investigator and Helper helps with reading and identification of the noise frequencies; slide 3&4. This program takes the signal from mic and plot it on the wave form graph than it does FFT to distinguish the different frequencies in the signal with their relative power in DB. This program can also write and read the data for future use. Helper part of the program can helps in many ways; it can help with deciding which material is better for certain frequency range, it can help with deciding which setup is better and it can also help with choosing that which part on optical table has less mechanical noise. It does it by feeding the power values of particular frequency from FFT power spectrum graph into an array and then taking a mean and feeding it into an another array (you can choose your desired name for that value and feed it). Than the whole process is repeated again for different frequencies and compare the values in the last.
Tone generator is another program of this setup; slide 5. It can generate a tone of any frequency, but it does not matter because every electronics and output device (speaker) have its own frequency response range, so only the frequencies in that range will workout. This program is helpful with testing of frequency response of different materials and setups. Now for example I can generate a range of frequencies to test the mechanical frequency response of the optical table at certain distance or place on the table. Same can be done with microscope or other stages or breadboards or different isolation materials/setups by reading the generated signal through AMNR.
Demonstration
{{#widget:YouTube|id=OvnHOqQuTc4}}
