Hi all,
First time posting on this forum. I am fairly new to DIY electronics so I apologize for the simple questions I am going to ask.
I am trying to make a cheap ultrasonic mic (that works up to about 50Khz) that I can use with my E-mu Tracker usb mic pre. (24 bit, 192khz AD converter with mic pre and 48V phantom power, 1.5K mic input impedence).
I purchased several Knowles SPM0404UD5 ultrasonic sensors with the idea of trying to get them to work with the usb mic pre. These pieces operate at 3.6V/250uA (max) .
Would there be any issue using the 48V phantom power coming off the mic pre (by just using a voltage divider or some sort of regulator circuit)? If not could I just use two 1.5V AA batteries to get 3V? Should I be able to use these SPM0404 sensors with a typical microphone preamp like the Tracker? I dont want to fry anything. Having hard time knowing where to begin being a newbie and all.
Knowles ultrasonic mic SPM0404UD5 will soon reach end-of-life (EOL) and not be in production anymore. The deadline for making any last-time purchases is in November. Please contact me if you need to purchase this microphone.
Suggested replacement microphones with similar performance are the SPU series of mics from Knowles. http://www.knowles.com/search/product.htm?x_sub_cat_id=3
As a kid in my radio days I remember hearing the ultra high frequency sounds from capacitors. Coupled with Beau's idea, all you need is a tuned capacitor.
Davin,
I looked at the SPU series, but the frequency response curves on the data sheets available at the Knowles site go only up to 10kHz. Is there one specifically SiSonic series that replaces the SPM0404UD5 at ultrasonic frequencies? I did receive an obsolete part notice from Digikey back in June, but the link for replacements is empty. How do we contact you?
Knowles ultrasonic mic SPM0404UD5 will soon reach end-of-life (EOL) and not be in production anymore. The deadline for making any last-time purchases is in November. Please contact me if you need to purchase this microphone.
Suggested replacement microphones with similar performance are the SPU series of mics from Knowles. http://www.knowles.com/search/product.htm?x_sub_cat_id=3
For most north American bats something that works from 20K to about 100K will get the base tones and most of the harmonics. 150K should get all the rest. Below 20K will mostly get you insects and noise. You can find some example frequencies at the University of New Mexico call library http://www.msb.unm.edu/mammals/batcall/html/calllibrary.html Some other microphones you might look at for around $130 US is http://www.titley-scientific.com/au/index.php/anabat-bat-detector. These are commonly used for zero-crossing detectors but should also work on heterodyne as well.
My grandparents had this really old B+W TV set
in the den that made a horrible high pitched tone
whenever it was on. I bet this bat detector would
have detected it.
They thought I was goofy until I had them turn the set
off and on and I stood outside the room. I could tell
them when the TV was on or off by the tone. They
could not hear it.
Yes, many tube TV were 'audible' to me like that. A very faint hiss that lots of others thought I was crazy for saying I could hear.
Knowles does have a substitute for the EOL SPM0404UD5. It is the SPU0410R5H, data sheet attached, and see figure 7b for the ultrasonic characterization. $3.92 qty 1 from Digikey. The response, like the earlier one, has lots of ups and downs and could benefit from serious equalization. And it falls off rapidly above 70kHz.
Knowles does have a substitute for the EOL SPM0404UD5. It is the SPU0410R5H, data sheet attached, and see figure 7b for the ultrasonic characterization. $3.92 qty 1 from Digikey. The response, like the earlier one, has lots of ups and downs and could benefit from serious equalization. And it falls off rapidly above 70kHz.
You could equalize but most identification is based upon the fm sweep shape and ending frequency of the call/signal. For example a Pallid bat here in Northern Cal. might make three calls starting at ~77K down to ~30K with a characteristic shape. Only some of the most advanced analysis is using the power or amplitude of the call as part of the signature. While loud up close, the signal fades quickly with distance because of the high frequency so there are some practical limits on the distance at which one measures them. Even with the Titley and Petterson professional models most biologists plan to be within ~50-75 feet or so to get a good signal. That said, there is a lot of room for advancing the signal processing and calibrating the measurements.
Gregg, I know you know what you are talking about, with your work with Cal Trans and bats under bridges. Thanks for that!
Bat detectors like the Titley Anabat record only the time between zero crossings of the signal, so the mic output is amplified like crazy and the recording picks up the strongest signal. But these days more and more detectors are using full spectrum recording with sampling at 192kHz up, and they log a wav file or something of that sort. A transducer and signal chain that has 20dB of sensitivity variation over the frequency range of interest will have quite an influence on the envelope of a frequency sweep and ultimately which bats can be detected, no matter what the back-end processing scheme. It is surprising to me that sensitivity vs frequency is not usually well reported for bat detectors and their microphones. That may be due to the difficulty of the measurement. It takes something like a good plasma speaker to generate a flat reference sweep at those frequencies.
Comments
First time posting on this forum. I am fairly new to DIY electronics so I apologize for the simple questions I am going to ask.
I am trying to make a cheap ultrasonic mic (that works up to about 50Khz) that I can use with my E-mu Tracker usb mic pre. (24 bit, 192khz AD converter with mic pre and 48V phantom power, 1.5K mic input impedence).
http://www.creative.com/emu/products/product.aspx?category=610&pid=17511
I purchased several Knowles SPM0404UD5 ultrasonic sensors with the idea of trying to get them to work with the usb mic pre. These pieces operate at 3.6V/250uA (max) .
http://www.knowles.com/search/prods_pdf/SPM0404UD5.PDF
Would there be any issue using the 48V phantom power coming off the mic pre (by just using a voltage divider or some sort of regulator circuit)? If not could I just use two 1.5V AA batteries to get 3V? Should I be able to use these SPM0404 sensors with a typical microphone preamp like the Tracker? I dont want to fry anything. Having hard time knowing where to begin being a newbie and all.
Any feedback appreciated!
Suggested replacement microphones with similar performance are the SPU series of mics from Knowles. http://www.knowles.com/search/product.htm?x_sub_cat_id=3
Regards,
Davin Moorman
I looked at the SPU series, but the frequency response curves on the data sheets available at the Knowles site go only up to 10kHz. Is there one specifically SiSonic series that replaces the SPM0404UD5 at ultrasonic frequencies? I did receive an obsolete part notice from Digikey back in June, but the link for replacements is empty. How do we contact you?
Yes, many tube TV were 'audible' to me like that. A very faint hiss that lots of others thought I was crazy for saying I could hear.
The Titley Scientific microphones are capacitance type, as are the Senscomp transducers.
You could equalize but most identification is based upon the fm sweep shape and ending frequency of the call/signal. For example a Pallid bat here in Northern Cal. might make three calls starting at ~77K down to ~30K with a characteristic shape. Only some of the most advanced analysis is using the power or amplitude of the call as part of the signature. While loud up close, the signal fades quickly with distance because of the high frequency so there are some practical limits on the distance at which one measures them. Even with the Titley and Petterson professional models most biologists plan to be within ~50-75 feet or so to get a good signal. That said, there is a lot of room for advancing the signal processing and calibrating the measurements.
Bat detectors like the Titley Anabat record only the time between zero crossings of the signal, so the mic output is amplified like crazy and the recording picks up the strongest signal. But these days more and more detectors are using full spectrum recording with sampling at 192kHz up, and they log a wav file or something of that sort. A transducer and signal chain that has 20dB of sensitivity variation over the frequency range of interest will have quite an influence on the envelope of a frequency sweep and ultimately which bats can be detected, no matter what the back-end processing scheme. It is surprising to me that sensitivity vs frequency is not usually well reported for bat detectors and their microphones. That may be due to the difficulty of the measurement. It takes something like a good plasma speaker to generate a flat reference sweep at those frequencies.