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I'm currently researching bat social calls (not echolocation calls) and have been given a series of samples (in .wav format) and wanted to know if what I can hear is actually the social calls. Below is a Graph representation of the a sample from the data I have:

enter image description here

This looks fine to me. From this, I can clearly tell where the social calls are. If I play at the specific peaks, then it sounds like a bat "chirping." However, I've been told that social calls cannot be played back, and, therefore humans cannot hear them. I'm just trying to figure out what these noises, or, chirps might actually be.

Here is a link to the .wav file:

Thanks for your help :)

theforestecologist
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Phorce
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  • Come on, edit your question and ask it. – Chris Jan 06 '14 at 23:01
  • Ha ha! Yes it seems at first sight that such question would fit this website. So, as @Chris said, edit this question (including the title) and directly ask your question on bats and social calls. – Remi.b Jan 06 '14 at 23:03
  • @user1326876 Have you gotten any explanation other than "its impossible" why you cannot record the social calls? – Chris Jan 06 '14 at 23:27
  • @Chris - The social calls are recorded. I was told "it's impossible" to play the social calls back, since, they were recorded real-time and cannot be detected with just a standard media player.. But if this is the case, what am I hearing when playing these files back? – Phorce Jan 06 '14 at 23:33

1 Answers1

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It could not fit in a comment..

You recorded bats. You are interested in social calls. Socials calls can be recorded by your microphone but they cannot be read by standard media player because...

  • the standard media player are limited to certain frequencies
  • your speakers cannot produce such high sounds
  • your ears are not able to hear many of the frequencies emitted
  • you formatted your records in a format that cannot hold very high frequency (for reason of optimizing data compression)

You might use some program like Adobe Audition in order to easily visualize the frequencies (vs time) of your record. (It might also help you finding all harmonics or performing Fourrier analysis)

This wiki article says :

Social Calls

This is a wide subject and there is still a lot to be discovered about bat social communication and how they use social calls in roosts and when flying. Generally a bat social call is not tonal, in other words it does not consist of a musical type note. Some bat detectors do not produce an accurate recording of a bat social call. Typically bat social calls use a lower frequency range than echolocation calls, and can thus be heard further away. Sometimes a bat will make a social call while echolocating which can cause confusion.

We can see and hear how the lower frequency social calls are heard at a greater distance than the higher echolocation calls as the bat approaches and departs. Zooming in on a spectrogram, social calls are atonal and repeated rapidly about five times in each call. The social calls are interleaved between the echolocation calls. They show a ragged frequency distribution around 20 kHz. Note the FD detector divides frequencies by 10. The echolocation calls are single "hockey stick" calls at a higher repetition rate. At this scale the hockey stick shape is not very clear, but the end frequency can be measured as 45.2 kHz. A doppler shift is recorded as the bat approaches. The frequency was measured as it passes

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Remi.b
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  • I believe the first one. But, if this is the case. In the sample I gave in my post. What is it exactly I'm hearing? I have performed the a FFT on the signal, but, it still does not give any indication to where the social calls actually are. – Phorce Jan 07 '14 at 00:36
  • For example, could it be that the person who has recorded these bat samples has already made it possible to hear the calls? – Phorce Jan 07 '14 at 00:43
  • You want to know when you hear socail calls. Well, if social calls of your bats are around 20 kHz (at what frequency do you expect to find these calls?), then you might find signals on the frequency spectrum around 20 kHz. If someone modified the records by shifting the frequencies, he would have probably notice it somewhere. That would be surprising. But the best is always to contact the dude who took these records – Remi.b Jan 07 '14 at 00:43
  • Okay, thanks! I'll take a look at the FFT and see if anything comes up at the specific frequency range. Is there a chart or something for different kinds of bats at what frequency they can be heard at? – Phorce Jan 07 '14 at 00:45
  • I am affraid there not enough study to create such a chart (But I don't know much!). you may try this article though. If you know which species you're dealing with you may find some studies that compared individual-specific or group-specific social calls – Remi.b Jan 07 '14 at 01:05
  • Thanks, but, this does not answer my question. What exactly can I/you hear from the recording I posted? If they are not social calls, what are they? – Phorce Jan 07 '14 at 01:25
  • Did you have a look on this two Wikipedia articles (I know, its not a scientific ressource but sometimes a good starting point): Bat species identification and Bat detector. They go into some of the details discussed here. – Chris Jan 07 '14 at 07:35
  • I know it does not answer. I don't quite know to what frequency these sounds we can hear correspond. But anyway, I would recommend to you to contact the guy who made the record he will probably manage to help you a lot. – Remi.b Jan 07 '14 at 09:19