A meta-analysis of the effects in alpha acoustic indices

doi:10.17520/biods.2022369

Abstract

Abstract:

Background: Many animals such as mammals, birds, amphibians, fishes and arthropods, produce sounds when moving, communicating or sensing their environment. Building upon the rich legacies of bioacoustics and animal communication, the acoustic properties from soundscape are used to monitor and assess the changes in animal communities and related environments. During the past decade, many acoustic indices have been developed and can be divided into two categories, namely alpha acoustic indices and beta acoustic indices. Alpha acoustic indices reflect the information in the recording while beta acoustic indices focus on comparison of differences between different recordings. There are far more empirical studies of the application of alpha acoustic indices than beta acoustic indices. However, patterns in alpha acoustic indices have been contradictory. Before alpha indices can be applied widely, it is necessary to understand better how well they reflect the communities and the environments to be monitored.

Aims: To make general inferences from the mixed evidence, associations between alpha acoustic indices and animal diversity, habitat quality, animal activity were quantitatively reviewed based on the meta-analytic approach.

Methods: Both key word searches and cross-reference searches were conducted, and 2,845 pairs of data related to alpha acoustic indices and other variables were collected from 136 references. For the alpha acoustic indices which were used more than 50 times, the direction of their associations was tested by sign test. Then, the maximum likelihood method was employed to estimate the probability density function of the summary effect (i.e., the correlation coefficient between the alpha acoustic index and other variable). Lastly, the correlation coefficients were calculated based on the probability density function.

Results & Conclusion: Eight commonly used alpha acoustic indices were involved in the study, namely acoustic complexity index (ACI), acoustic entropy index (H) (including two closely related indices: temporal entropy and spectral entropy index), bioacoustic index (BI), normalized difference soundscape index (NDSI), acoustic diversity index (ADI), acoustic evenness index (AEI), acoustic richness index (AR), and number of peaks (NP). Among these acoustic indices, ACI was the most frequently used and positively related with animal diversity, habitat quality, and animal activity. The highest association coefficient appeared at the relationship between ACI and terrestrial animal activity, with the mean effect size 0.53. Besides, the correlation coefficients in other acoustic indices were always trivial, with the effect sizes generally less than 0.30. The only significantly negative relationship occurred between AEI and terrestrial habitat quality, with the mean effect size ‒0.18. The robustness of the main results was thoroughly analyzed, and the strengths and weaknesses of acoustic monitoring through acoustic indices were also discussed. This study is expected to provide a guideline for the selection of alpha acoustic indices in future research.

Key words: acoustic index, biodiversity, animal activity, habitat quality, meta-analysis

Yanyi Wang, Yimei Zhang, Canwei Xia, Anders Pape Møller. A meta-analysis of the effects in alpha acoustic indices[J]. Biodiv Sci, 2023, 31(1): 22369.

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URL: https://www.biodiversity-science.net/EN/10.17520/biods.2022369

https://www.biodiversity-science.net/EN/Y2023/V31/I1/22369

Figures/Tables 7

Table 1 Description of the commonly used alpha acoustic indices

声学指数 Acoustic index	计算公式 Computing formula	描述 Description	参考文献 Reference
声学复杂度指数 Acoustic complexity index (ACI)	$D / ∑ ? I k$	相邻频段窗口音量的变化; 相邻频段音量差的累积(D); 各频段的音量(I_k) The difference in amplitude among samples; summary of intensity difference among adjacent frequency bins (D); intensity in a single frequency bin (I_k)	2011
声学多样性指数 Acoustic diversity index (ADI)	Σp_i×logp_i	基于Shannon指数量化音量(p_i)在不同频段的分布 Reflection of spectral complexity based on Shannon index; relative intensity in each frequency bin (p_i)	2011
声学均匀度指数 Acoustic evenness index (AEI)	$G i n i I$	基于Gini指数量化音量(I)在不同频段的分布 Gini coef?cient with intensity (I) at each frequency bin	2011
声学丰富度指数 Acoustic richness index (AR)	[rank(H_t) × rank(M)]/n²	时间熵(H_t)和音量(M)的乘积, 除以频段数量(n) Product of time entropy (H_t) and intensity (M) divided by the number of bins (n)	2012
生物声学指数 Bioacoustic index (BI)	$∑ ? I k$	特定频段音量(I_k)的汇总 The sum of amplitude (I_k) in particular frequency band	2007
声学熵指数 Acoustic entropy index (H)	H_t × H_f	时间熵(H_t)和频谱熵(H_f)的乘积 Product of time entropy (H_t) and spectral entropy (H_f)	2008
标准化声景差异指数 Normalized difference soundscape index (NDSI)	$b ? a b + a$	生物产生音量(b)与人类产生音量(a)的比率 Ratio of amplitude in biophony (b) and anthropophony (a)	2012
频峰数 Number of peaks (NP)	Σf_i	频谱上频峰(f_i)的数量 The number of frequency peaks (f_i) on spectrum	2013

Table 1 Description of the commonly used alpha acoustic indices

声学指数 Acoustic index	计算公式 Computing formula	描述 Description	参考文献 Reference
声学复杂度指数 Acoustic complexity index (ACI)	$D / ∑ ? I k$	相邻频段窗口音量的变化; 相邻频段音量差的累积(D); 各频段的音量(I_k) The difference in amplitude among samples; summary of intensity difference among adjacent frequency bins (D); intensity in a single frequency bin (I_k)	2011
声学多样性指数 Acoustic diversity index (ADI)	Σp_i×logp_i	基于Shannon指数量化音量(p_i)在不同频段的分布 Reflection of spectral complexity based on Shannon index; relative intensity in each frequency bin (p_i)	2011
声学均匀度指数 Acoustic evenness index (AEI)	$G i n i I$	基于Gini指数量化音量(I)在不同频段的分布 Gini coef?cient with intensity (I) at each frequency bin	2011
声学丰富度指数 Acoustic richness index (AR)	[rank(H_t) × rank(M)]/n²	时间熵(H_t)和音量(M)的乘积, 除以频段数量(n) Product of time entropy (H_t) and intensity (M) divided by the number of bins (n)	2012
生物声学指数 Bioacoustic index (BI)	$∑ ? I k$	特定频段音量(I_k)的汇总 The sum of amplitude (I_k) in particular frequency band	2007
声学熵指数 Acoustic entropy index (H)	H_t × H_f	时间熵(H_t)和频谱熵(H_f)的乘积 Product of time entropy (H_t) and spectral entropy (H_f)	2008
标准化声景差异指数 Normalized difference soundscape index (NDSI)	$b ? a b + a$	生物产生音量(b)与人类产生音量(a)的比率 Ratio of amplitude in biophony (b) and anthropophony (a)	2012
频峰数 Number of peaks (NP)	Σf_i	频谱上频峰(f_i)的数量 The number of frequency peaks (f_i) on spectrum	2013

Fig. 1 Summary of the process used to collect, quantify and analyze the origin research

Fig. 2 Frequency of use of acoustic index. Abbreviations are the same as denoted in Table 1.

Table 2 The association between acoustic index and animal diversity, habitat quality, animal activity

声学指数与关联变量 Acoustic index and associated variable^*	使用频次 Frequency of use	符号检验的显著性 P value based on sign test	beta分布的参数1 Parameter 1 in beta distribution	beta分布的参数2 Parameter 2 in beta distribution	效应量的均值 ± 标准差 Summary effect, mean ± SD	效应量的中位数 (下、上四分位数) Summary effect, median (lower and upper quartile)
ACI和陆地动物多样性 ACI and terrestrial animal diversity	127	< 0.001	3.14	1.70	0.30 ± 0.39	0.34 (0.02?0.61)
H和陆地动物多样性 H and terrestrial animal diversity	117	0.005	2.29	1.74	0.14 ± 0.44	0.16 (-0.19?0.49)
NDSI和陆地动物多样性 NDSI and terrestrial animal diversity	81	< 0.001	5.97	4.19	0.18 ± 0.29	0.19 (-0.03?0.39)
ADI和陆地动物多样性 ADI and terrestrial animal diversity	73	0.053	2.73	2.17	0.11 ± 0.41	0.13 (-0.19?0.43)
BI和陆地动物多样性 BI and terrestrial animal diversity	69	< 0.001	7.89	5.76	0.16 ± 0.26	0.16 (-0.02?0.34)
AEI和陆地动物多样性 AEI and terrestrial animal diversity	67	0.864	2.52	2.62	-0.02 ± 0.40	-0.02 (-0.32?0.28)
ACI和陆地生境质量 ACI and terrestrial habitat quality	445	0.001	7.92	7.18	0.05 ± 0.25	0.05 (-0.13?0.22)
BI和陆地生境质量 BI and terrestrial habitat quality	119	0.868	5.83	5.94	-0.01 ± 0.28	-0.01 (-0.21?0.19)
NDSI和陆地生境质量 NDSI and terrestrial habitat quality	116	< 0.001	5.37	4.07	0.14 ± 0.31	0.15 (-0.08?0.36)
ADI和陆地生境质量 ADI and terrestrial habitat quality	103	0.005	3.38	2.62	0.13 ± 0.37	0.14 (-0.14?0.41)
AEI和陆地生境质量 AEI and terrestrial habitat quality	82	0.001	2.39	3.41	-0.18 ± 0.38	-0.20 (-0.47?0.09)
H和陆地生境质量 H and terrestrial habitat quality	59	0.052	5.44	4.45	0.10 ± 0.30	0.11 (-0.11?0.32)
ACI和陆地动物活跃程度 ACI and terrestrial animal activity	86	< 0.001	1.95	0.60	0.53 ± 0.45	0.67 (0.26?0.90)
ACI和水生动物多样性 ACI and aquatic animal diversity	51	0.004	6.72	4.96	0.15 ± 0.28	0.16 (-0.04?0.35)
ACI和水生生境质量 ACI and aquatic habitat quality	75	0.035	11.08	9.41	0.08 ± 0.22	0.08 (-0.07?0.23)
ACI和水生动物活跃程度 ACI and aquatic animal activity	87	< 0.001	9.06	5.97	0.20 ± 0.24	0.22 (0.04?0.38)

Table 2 The association between acoustic index and animal diversity, habitat quality, animal activity

声学指数与关联变量 Acoustic index and associated variable^*	使用频次 Frequency of use	符号检验的显著性 P value based on sign test	beta分布的参数1 Parameter 1 in beta distribution	beta分布的参数2 Parameter 2 in beta distribution	效应量的均值 ± 标准差 Summary effect, mean ± SD	效应量的中位数 (下、上四分位数) Summary effect, median (lower and upper quartile)
ACI和陆地动物多样性 ACI and terrestrial animal diversity	127	< 0.001	3.14	1.70	0.30 ± 0.39	0.34 (0.02?0.61)
H和陆地动物多样性 H and terrestrial animal diversity	117	0.005	2.29	1.74	0.14 ± 0.44	0.16 (-0.19?0.49)
NDSI和陆地动物多样性 NDSI and terrestrial animal diversity	81	< 0.001	5.97	4.19	0.18 ± 0.29	0.19 (-0.03?0.39)
ADI和陆地动物多样性 ADI and terrestrial animal diversity	73	0.053	2.73	2.17	0.11 ± 0.41	0.13 (-0.19?0.43)
BI和陆地动物多样性 BI and terrestrial animal diversity	69	< 0.001	7.89	5.76	0.16 ± 0.26	0.16 (-0.02?0.34)
AEI和陆地动物多样性 AEI and terrestrial animal diversity	67	0.864	2.52	2.62	-0.02 ± 0.40	-0.02 (-0.32?0.28)
ACI和陆地生境质量 ACI and terrestrial habitat quality	445	0.001	7.92	7.18	0.05 ± 0.25	0.05 (-0.13?0.22)
BI和陆地生境质量 BI and terrestrial habitat quality	119	0.868	5.83	5.94	-0.01 ± 0.28	-0.01 (-0.21?0.19)
NDSI和陆地生境质量 NDSI and terrestrial habitat quality	116	< 0.001	5.37	4.07	0.14 ± 0.31	0.15 (-0.08?0.36)
ADI和陆地生境质量 ADI and terrestrial habitat quality	103	0.005	3.38	2.62	0.13 ± 0.37	0.14 (-0.14?0.41)
AEI和陆地生境质量 AEI and terrestrial habitat quality	82	0.001	2.39	3.41	-0.18 ± 0.38	-0.20 (-0.47?0.09)
H和陆地生境质量 H and terrestrial habitat quality	59	0.052	5.44	4.45	0.10 ± 0.30	0.11 (-0.11?0.32)
ACI和陆地动物活跃程度 ACI and terrestrial animal activity	86	< 0.001	1.95	0.60	0.53 ± 0.45	0.67 (0.26?0.90)
ACI和水生动物多样性 ACI and aquatic animal diversity	51	0.004	6.72	4.96	0.15 ± 0.28	0.16 (-0.04?0.35)
ACI和水生生境质量 ACI and aquatic habitat quality	75	0.035	11.08	9.41	0.08 ± 0.22	0.08 (-0.07?0.23)
ACI和水生动物活跃程度 ACI and aquatic animal activity	87	< 0.001	9.06	5.97	0.20 ± 0.24	0.22 (0.04?0.38)

Fig. 3 Probability density function about the correlation coefficients between terrestrial animal diversity and acoustic index ACI (A), H (B), NDSI (C), ADI (D), BI (E), AEI (F). Abbreviations are the same as denoted in Table 1.

Fig. 4 Probability density function about the correlation coefficients between terrestrial habitat quality and acoustic index ACI (A), BI (B), NDSI (C), ADI (D), AEI (E), H (F). Abbreviations are the same as denoted in Table 1.

Fig. 5 Probability density function about the correlation coefficients between acoustic complexity index (ACI) and terrestrial animal activity (A), aquatic animal diversity (B), aquatic habitat quality (C), aquatic animal activity (D)

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