<p>In the noise monitoring world, we regularly look at <a href="https://www.sciencedirect.com/topics/engineering/third-octave" rel="nofollow noreferrer">Third-octave Levels</a> (TOLs) to describe the soundscape, especially in the lower frequencies you are interested in. We use them to help describe increases in anthropogenic pressure</p>
<p>The linked article can be found in:</p>
<p>Meggitt, J. A. R. (2017). On in-situ methodologies for the characterisation and simulation of vibro-acoustic assemblies. University of Salford (United Kingdom).</p>

CC BY-SA 4.0
2022-07-06T07:00:09.203Z
2022-07-06T07:00:09.203Z
etgriffiths
<p>I suppose you can calculate any acoustic index just on the smaller bin - ie get seewave to calculate for example ACI in the limited range.</p>
<p>Or downsample to 4 or 8 khz and then run your normal scripts in R.</p>

CC BY-SA 4.0
2022-07-07T08:13:41.700Z
Number of bins won't be preserved _unless_ you downsample, or you change the window length to match the equivalent spectrogram resolution found in the original recording.
EcologyTom
CC BY-SA 4.0
2022-07-06T06:07:03.377Z
Please avoid using unexplained abbreviations. Not all users will know what ACI is.
etgriffiths
CC BY-SA 4.0
2022-07-06T06:39:46.483Z
Thanks Simon.  My thought/concern is that by reducing the analysis bandwidth of the Acoustic Complexity Index, I am also reducing the number of frequency bins used in the index (to only two?), and thereby reducing the power of the index??
Carlos Abrahams
CC BY-SA 4.0
2022-07-07T00:11:32.707Z
We have to ask Jerome Sueur. I think the number of frequency bins are preserved. Definitely if you downsample ahead of time they should be preserved.
Simon Linke
CC BY-SA 4.0
2022-07-06T06:02:35.290Z
2022-07-06T06:02:35.290Z
Simon Linke
<p>You might check out the methods used in these papers -</p>
<p><a href="https://www.sciencedirect.com/science/article/pii/S004896972203073X" rel="nofollow noreferrer">Non-native species change the tune of tundra soils: Novel access to soundscapes of the Arctic earthworm invasion</a>.</p>
<p><a href="https://www.researchgate.net/publication/335826299_Sounding_Soil_An_Acoustic_Ecological_Artistic_Investigation_of_Soil_Life" rel="nofollow noreferrer">Sounding Soil: An Acoustic, Ecological &amp; Artistic Investigation of Soil Life</a></p>
<p>And as alluded to in previous comments, you could also just run a bandpass filter and calculate the indices on the filtered recordings.</p>

CC BY-SA 4.0
2022-07-06T15:34:56.320Z
2022-07-06T15:34:56.320Z
Carly Batist
<p>We are currently analysing soil recordings using Acoustic Indices, and applying Acoustic Complexity Index to the 0-2 kHz range (there is no useful signal above this upper limit).  The Acoustic Complexity Index (ACI) is as proposed in Pieretti, Farina &amp; Morri (2011) A new methodology to infer the singing activity of an avian community: The Acoustic Complexity Index (ACI) Ecological Indicators 11(3)</p>
<p>Which other Indices could be usefully applied below the 2 kHz upper limit?</p>
<p>Is anyone aware of studies applying Indices in narrow frequency ranges like this?</p>
<p>Thanks</p>

CC BY-SA 4.0
2022-07-06T00:18:59.200Z
Could you include a reference to the 'acoustic indices' and 'acoustic complexity index' that you're referring to? It might be helpful if you explained a bit more about your research questions so community members might be able to give you other suggestions.
ASimonis
CC BY-SA 4.0
2022-07-06T06:36:40.883Z
Thanks.  The Acoustic Complexity Index (ACI) is as proposed in Pieretti, Farina & Morri (2011) A new methodology to infer the singing activity of an avian community: The Acoustic Complexity Index (ACI) Ecological Indicators 11(3)
Carlos Abrahams
<acoustic-indices>
Which Acoustic Indices are useful for low-frequency recordings?
# Which Acoustic Indices are useful for low-frequency recordings?

(Asked by: username_0 on 2022-07-05)

We are currently analysing soil recordings using Acoustic Indices, and applying Acoustic Complexity Index to the 0-2 kHz range (there is no useful signal above this upper limit). The Acoustic Complexity Index (ACI) is as proposed in Pieretti, Farina & Morri (2011) A new methodology to infer the singing activity of an avian community: The Acoustic Complexity Index (ACI) Ecological Indicators 11(3)

Which other Indices could be usefully applied below the 2 kHz upper limit?

Is anyone aware of studies applying Indices in narrow frequency ranges like this?

Thanks

**Tags:** acoustic-indices

> **Comments:**
> **username_1**: Could you include a reference to the 'acoustic indices' and 'acoustic complexity index' that you're referring to? It might be helpful if you explained a bit more about your research questions so community members might be able to give you other suggestions.  
> **username_0**: Thanks.  The Acoustic Complexity Index (ACI) is as proposed in Pieretti, Farina & Morri (2011) A new methodology to infer the singing activity of an avian community: The Acoustic Complexity Index (ACI) Ecological Indicators 11(3)  

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## 3 answers

### Answer by username_2 on 2022-07-06. Score: 3

In the noise monitoring world, we regularly look at [Third-octave Levels](https://www.sciencedirect.com/topics/engineering/third-octave) (TOLs) to describe the soundscape, especially in the lower frequencies you are interested in. We use them to help describe increases in anthropogenic pressure

The linked article can be found in:

Meggitt, J. A. R. (2017). On in-situ methodologies for the characterisation and simulation of vibro-acoustic assemblies. University of Salford (United Kingdom).


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### Answer by username_3 on 2022-07-06. Score: 2

I suppose you can calculate any acoustic index just on the smaller bin - ie get seewave to calculate for example ACI in the limited range.

Or downsample to 4 or 8 khz and then run your normal scripts in R.

> **Comments:**
> **username_2**: Please avoid using unexplained abbreviations. Not all users will know what ACI is.  
> **username_0**: Thanks username_3.  My thought/concern is that by reducing the analysis bandwidth of the Acoustic Complexity Index, I am also reducing the number of frequency bins used in the index (to only two?), and thereby reducing the power of the index??  
> **username_3**: We have to ask Jerome Sueur. I think the number of frequency bins are preserved. Definitely if you downsample ahead of time they should be preserved.  
> **username_4**: Number of bins won't be preserved _unless_ you downsample, or you change the window length to match the equivalent spectrogram resolution found in the original recording.  

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### Answer by username_5 on 2022-07-06. Score: 2

You might check out the methods used in these papers -

[Non-native species change the tune of tundra soils: Novel access to soundscapes of the Arctic earthworm invasion](https://www.sciencedirect.com/science/article/pii/S004896972203073X).

[Sounding Soil: An Acoustic, Ecological & Artistic Investigation of Soil Life](https://www.researchgate.net/publication/335826299_Sounding_Soil_An_Acoustic_Ecological_Artistic_Investigation_of_Soil_Life)

And as alluded to in previous comments, you could also just run a bandpass filter and calculate the indices on the filtered recordings.


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