Ecoacoustics 2016

2016/6/5-8 @ University of Michigan

Investigation on the dynamics of soundscape by using unsupervised detection and classification algorithms

Tzu-Hao Lin, Lien-Siang Chou
Institute of Ecology and Evolutionary Biology, National Taiwan University, Repubic of China (Taiwan)

Yu-Huang Wang
Biodiversity Research Center, Academia Sinica, Repubic of China (Taiwan)

Soundscape has been proposed as a potential information source to study the variability of biodiversity. However, analysis of the soundscape is a challenging task when there is no sufficient database to recognize various sounds collected from long duration recordings. Previous researches have measured several acoustic diversity indexes to quantify the variation of biodiversity, but the acoustic diversity indexes are still difficult to interpret without any ground truth. In this study, we propose to analyze the composition of soundscape scenes and visualize the dynamics of soundscape by using unsupervised detection and classification algorithms. Different soundscape scenes were classified according to the tonal sounds, pulsed sounds, and acoustic features obtained from long-term spectrogram. By adjusting the variation explained through classification results, the number of soundscape scenes will be automatically determined. The unsupervised classifier has been employed to analyze the soundscape dynamics in several forests and shallow marine environments in Taiwan. Our results demonstrate that the seasonal and diurnal changing patterns of geophony, biophony, and anthrophony can be effectively investigated. Besides, the spatial change of soundscape can also be discriminated according to the composition of soundscape scenes. After the biophony scenes have been identified, we can apply the same classifier again to measure the complexity of biological sounds and examine the variability of biodiversity. The current approach provides researchers and managers a visualization platform to monitor the dynamics of soundscape and to study the interactions among acoustic environment, biodiversity, and human activities in the future.

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2016年臺灣地球科學聯合學術研討會

2016/5/20

近海與海岸環境 Land-Ocean Interactions in the Changing Coastal Zones of Taiwan:
Scientific Basis and Societal Engagements

應用非監督式分類方法調查海洋聲景的時空變化

林子皓
國立台灣大學生態學與演化生物學研究所

海洋聲景由環境音、動物聲音與人為噪音所組成,是由各種水下聲音所構築而成的音響環境。環境音可能來自於風浪、海流、地震等等自然事件,受到海床地形、水文的變化,聲音在各地傳播的路徑有所不同,進而塑造出獨特的音響環境。動物音主要來自於海洋動物發聲,也可能來自動物移動過程或水面活動伴隨發出的聲音。動物音具有高度複雜的變異性,以鯨豚和魚類為例,不同種的聲音特徵有所差別,但同種的聲音卻也有可能受到行為影響而有著不同的結構。海域的人為噪音則以船隻交通、海洋工程的噪音為主,依據接受強度的不同,噪音可能會使動物受到生理傷害、干擾行為、遮蔽溝通,長期暴露下也可能增加免疫壓力。因此,調查海洋聲景不只可以協助我們了解海洋環境特性、海洋動物的種類組成與活動特性,更可以了解人為噪音對海洋生態的影響。近年來隨著水下技術的發展,國際上開始廣泛應用自動錄音機收集長時間水下錄音調查海洋聲景的時空變化。然而目前仍缺乏完整資料庫辨認各種聲音,也難以利用人工分析巨量錄音,因此阻礙了海洋聲景生態學的發展。本研究運用資訊分析技術,解析海洋聲景的事件組成,以進一步了解海洋環境與生態的動態變化。在野外取回水下錄音之後,計算每五分鐘水下錄音的平均功率頻譜,以壓縮大量的錄音資料,並將一系列的平均功率頻譜組合成長期時頻譜圖做為視覺化分析海洋聲景的基礎資料。此外,將每五分鐘的平均功率頻譜作為分析參數,經過多變數分析方法減少特徵向量的維度之後,利用區分資料在多重維度空間內的分佈叢集,作為非監督式分類海洋聲景事件的分析架構。本研究應用自行開發的演算法分析苗栗中港溪口附近海域的水下錄音資料,結果顯示海洋聲景的事件組成在以泥沙底質為主的河口海域以及礁石為主的人工魚礁附近有明顯的結構性差異。海洋聲景在河口海域以較為安靜的環境音、以及夜晚出現的石首魚群鳴唱為主,但在人工魚礁附近則是以吵雜的槍蝦聲音、以及傍晚過後出現的低頻魚群鳴音為主要的事件。透過視覺化分析海洋聲景事件組成的時序變化,將可協助海洋生態研究人員進一步了解各地的海洋動物群聚組成與生態系統的動態變化,並提供海洋生態保育經營的重要基礎資料。

Oceanoise Asia 2016

2016/4/20

Characterization of the marine soundscape at the core habitat of Indo-Pacific humpback dolphins

Tzu-Hao Lin, Lien-Siang Chou
Institute of Ecology and Evolutionary Biology, National Taiwan University

Shane Guan
Office of Protected Resources, National Marine Fisheries Service, Silver Spring, MD, USA

The soundscape in shallow waters displays a high level of spatial variation due to the difference in ocean environments, biological communities, and human activities. Many marine animals rely on sound for orientation; therefore, the soundscape has been hypothesized as one of the environmental indicators for marine animals. The population of Indo-Pacific humpback dolphins in western Taiwan waters is critically endangered. The anthropogenic noise might alter the marine soundscape evidently. However, the importance of soundscape for the habitat selection of cetacean remains unclear until now. In this study, underwater recorders were deployed in inshore waters to compare the difference of soundscape between the core habitat and non-core habitat of humpback dolphins. The result indicates that the composition of soundscape scene is different among our recording stations. At the core habitat, soundscape was characterized by the nighttime chorus of croakers and the quiet ambient sound in the daytime. On the contrary, snapping shrimp sounds represent the most dominated sound at the non-core habitats. The current result indicates that humpback dolphins prefer soundscape dominated by the chorus of their prey resources. The potential impacts of human activities on marine soundscape should be carefully evaluated in the future.

2016 動物行為暨生態研討會

2016/1/25-26

中華白海豚核心棲地的海洋聲景特徵以及保育經營的應用

林子皓、周蓮香

國立台灣大學生態學與演化生物學研究所

Shane Guan

美國國家海洋漁業局保護資源辦公室

海洋聲景由環境音、動物音以及人為噪音所組成,物理環境影響了聲音傳播,各地不同的動物群聚與人類活動也塑造出各種獨特的聲景。聲景中的訊息可讓海洋動物尋找適合的棲地,察知其他個體的活動位置,甚至探測獵物位置,因此可說是海洋動物生存的重要資源之一。台灣西部淺海的中華白海豚族群面臨許多威脅,水下噪音除了可能造成聽力損傷、行為干擾之外,也會改變當地的海洋聲景。但目前仍缺乏對白海豚棲地的聲景研究,也不清楚聲景的變化是否影響白海豚的棲地選擇。本研究於苗栗縣海域收集長時間水下聲音,分析時頻譜圖的時空變化,發現中港溪口的聲景與其他地區之間有明顯差異。中港溪口是中華白海豚的核心棲地,聲景以白天安靜的環境音和夜間吵雜的石首魚鳴唱為主。白海豚鮮少活動在龍鳳漁港外海的定置網區,以及外埔漁港外海的魚礁區,當地聲景則以槍蝦的寬頻脈衝聲與船隻噪音為主,石首魚的夜間鳴唱也較為低頻且不明顯。本研究結果顯示海洋聲景確實在白海豚核心與非核心棲地之間存在差異,高強度的石首魚鳴唱可能代表充足的食餌資源。未來除了可透過海洋聲景了解白海豚的潛在棲地,也可利用水下監聽站自動監測白海豚、石首魚與人為活動在各地海域的動態變化,以協助中華白海豚重要棲息環境的保育經營。

[聲物誌]台北藝術大學

[聲物誌]台北藝術大學

台北藝術大學位於北投區學園路的山丘上,由於校園內的景觀優美,又能從高點俯瞰關渡平原,早已經成為北投關渡地區的知名景點。但還記得12月初關於台北藝術大學校園內的石碑被更名為”台北藝術公園”的新聞嗎? 由於進入校內的遊客太多,加上校方在空間管理的政策未能和學生有效溝通,使得學生以此手段抗議「校園變公園、學殿變學店」的現象。

像是大學這種需要幽靜的環境,確實很容易受到湧入的人潮、辦理的活動而影響。假日進入到台北藝術大學,其實聽到的不是甚麼書香的聲音,往往聽到的是小孩放聲大叫、大人們嬉鬧聊天的聲音。

這些到底算不算噪音呢? 我想是因人而異。

但站在台北藝術大學的草地上,我發現除了遊客的聲音之外,其實有另外更值得大家關注、但也幾乎被所有人忽略的聲音:來自都市的低頻噪音

WP_20151205_16_19_58_Pro

我走到一處較為遠離遊客的山坡上,把我手上的錄音機朝向山坡上的一處草叢,除了遠方傳來的遊客交談聲,附近一處建築偶爾傳來的施工聲音、和後方經過的車聲之外,仔細聽會發現這裡有許多高頻、清脆、細微的蟲鳴聲。

但當我站在原地,把錄音機180度轉向關渡平原,驚人的事情發生了。大度路傳來的許多車聲、喇叭聲、松山機場起降的航班,取代蟲鳴聲成為了主角。和剛剛的聲音相比,背景中的低頻噪音非常明顯,雖然分不出確切的聲源,但可想而知應該是來自於台北的都會區。

fotor_(168).jpg

如果不是拿著錄音機這樣仔細地聽,其實我原本也沒有發覺原來聲音的感受在不同的角度有如此大的差別。這低頻的噪音一旦被意識抓住之後,短時間內很難不去注意它的存在。看著夕陽從關渡平原緩緩降下,聽著這截然不同的聲景,不禁想像如果台北的都會區能夠更安靜點,那我們的生活壓力是不是也會少了一點?

 

Conference presentation: 21st Biennial Conference on the Biology of Marine Mammals

13-18 Dec 2015

A noisy dinner? Passive acoustic monitoring on the predator-prey interactions between Indo-Pacific humpback dolphins and croakers

Tzu-Hao Lin, Wen-Ching Lien, Chih-Kai Yang, and Lien-Siang Chou
Institute of Ecology and Evolutionary Biology, National Taiwan University

Shane Guan
Office of Protected Resources, National Marine Fisheries Service, Silver Spring, MD, USA

The spatio-temporal dynamics of prey resources have been considered as important factors for shaping the distribution and behavior of odontocetes. Indo-Pacific humpback dolphin (Sousa chinensis) is a costal species, which primary feeds on benthic croakers. It has been hypothesized that the distribution pattern and periodic occurrence of humpback dolphins are results of their prey movement. However, the interactions between humpback dolphins and croakers remain unclear. During May 2013 and November 2014, underwater sound recordings were collected in western Taiwan waters. Croaker choruses and humpback dolphin echolocation clicks were automatically detected using custom developed algorithms. Both croaker choruses and dolphin clicks were frequently detected in shallow estuarine waters during spring and summer. In addition, shorter inter-click intervals were detected with higher frequencies in these areas, indicating more likely foraging behavior. Current results suggest that the core habitats of humpback dolphins show an agreement with the areas of prominent croaker chorus. Diurnal cycle analysis showed that croaker choruses were most evident after sunset to until approximately 4 A.M. In estuarine waters, humpback dolphin clicks were most frequently detected during the nighttime, with reduced detection rates after 8 A.M. This suggests that the diurnal behavior of humpback dolphins could be associated with the calling behavior of croakers. Although whether the position of a calling croaker could be passively localized by a dolphin remains unknown, our results indicate that the foraging probability of humpback dolphins may be elevated during the nighttime chorus of croakers. Information regarding the spatio-temporal dynamics of croaker chorus can be important for the conservation management of humpback dolphins. Further details on the predator-prey interactions between humpback dolphins and croakers can be investigated by using hydrophone arrays.

Poster (pdf)

[聲物誌] 北投農禪寺

北投農禪寺是北投地區相當著名的廟宇,尤其在水月道場改建之後,優美的景觀更吸引了許多人前往放鬆心情。

農禪寺

前一次造訪農禪寺時,就聽到法會中的唸佛聲。平常覺得唸佛的聲音頗為無趣,甚至讓人有點想睡,但許多人一起唸佛的聲音則有一種奇妙的感動,甚至就像一首交響樂一樣,讓人佇足於大殿之前,久久無法離去。

走到農禪寺著名的水月池前,看著寺裡的志工緩慢地一邊在池中走著、一邊清理著池底。雖然大殿內的唸佛聲仍然徘徊不去,偶爾也能夠聽見鳥鳴,但在這裡最常聽見的聲音卻是來自於大度路和洲美快速道路出口的車聲、喇叭聲。縱然水月道場的景觀優美,但卻無法抵擋百公尺之外的塵世的喧囂。

穿過金剛經牆到農禪寺的後方,眼界所及正是台北市少有的稻田景觀。一大片的青綠稻田被風吹拂著,稻草之間的摩擦聲也隨著風勢的強弱而上下起伏。不再被大量的車聲干擾,能夠真正地聽見這片土地的聲音,眼前雖然沒有堂皇的建築與令人驚豔的風景,但人在這裡,才真正地得以放鬆。

農禪寺位置

或許,當我們不斷地在保存文化資產、歷史古蹟與自然風景的同時,我們也該關懷耳朵中的聲景是不是也被保護了呢? 如果聲景沒有能夠妥善的保護,那我們又如何能夠真正的去欣賞風景呢?