Answers.Body: <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>
  
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Answers.UserDisplayName: etgriffiths
Answers.Body: <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>
  
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Answers.Text: 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.
Answers.UserDisplayName: EcologyTom
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Answers.Text: Please avoid using unexplained abbreviations. Not all users will know what ACI is.
Answers.UserDisplayName: etgriffiths
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Answers.Text: 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??
Answers.UserDisplayName: Carlos Abrahams
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Answers.Text: 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.
Answers.UserDisplayName: Simon Linke
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Answers.UserDisplayName: Simon Linke
Answers.Body: <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>
  
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Body: <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>
  
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Comments.CreationDate: 2022-07-06T00:18:59.200Z
Comments.Text: 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.
Comments.UserDisplayName: ASimonis
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Comments.CreationDate: 2022-07-06T06:36:40.883Z
Comments.Text: 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)
Comments.UserDisplayName: Carlos Abrahams
Tags: <acoustic-indices>
Title: Which Acoustic Indices are useful for low-frequency recordings?
ThreadText: # 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)  
  
  ---
  
  ## 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).
  
  
  ---
  
  ### 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 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??  
  > **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.  
  
  ---
  
  ### 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.
  
  
  ---
  
  