Forest Elephants Rumble Detection

Contains a collection of software packages for passive acoustic monitoring (PAM) of forest elephants rumbles.

The low fundamental frequencies of elephant rumbles are located at the bottom of the spectrogram and typically range from 14-35 Hz. These are the primary frequencies of the rumbles. Harmonics, which are integer multiples of the fundamental frequencies, appear as several horizontal lines above the fundamental frequency. For example, if the fundamental frequency is 20 Hz, the harmonics will be at 40 Hz, 60 Hz, 80 Hz, and so on. These harmonic lines are spaced at regular intervals and are usually less intense (lighter) than the fundamental frequency.

Introduction

Elephant rumbles are low-frequency vocalizations produced by elephants, primarily for communication. These rumbles are a fundamental part of elephant social interactions and serve various purposes within their groups. Here’s a detailed explanation:

Characteristics of Elephant Rumbles

1. Low Frequency: Elephant rumbles typically fall in the infrasound range, below 20 Hz, which is often below the threshold of human hearing. However, some rumbles can also be heard by humans as a low, throaty sound.

2. Long Distance Communication: Due to their low frequency, rumbles can travel long distances, sometimes several kilometers, allowing elephants to communicate with each other across vast areas, even when they are out of sight. It can also travel through dense forests as the wavelength is very large.

3. Vocal Production: Rumbles are produced by the larynx and can vary in frequency, duration, and modulation. Elephants use different types of rumbles to convey different messages.

Functions of Elephant Rumbles

1. Coordination and Social Bonding: Elephants use rumbles to maintain contact with members of their herd, coordinate movements, and reinforce social bonds. For example, a matriarch might use a rumble to lead her group to a new location.

2. Reproductive Communication: Male elephants, or bulls, use rumbles to communicate their reproductive status and readiness to mate. Females also use rumbles to signal their estrus status to potential mates.

3. Alarm and Distress Calls: Rumbles can signal alarm or distress, warning other elephants of potential danger. These rumbles can mobilize the herd and prompt protective behavior.

4. Mother-Calf Communication: Mothers and calves use rumbles to stay in contact, especially when they are separated. Calves may rumble to signal hunger or distress, prompting a response from their mothers.

Importance of Understanding Elephant Rumbles

1. Conservation Efforts: Understanding elephant communication helps in conservation efforts by providing insights into their social structure, habitat needs, and responses to environmental changes.

2. Human-Elephant Conflict Mitigation: By recognizing alarm rumbles, conservationists can better manage and mitigate conflicts between humans and elephants, especially in regions where their habitats overlap.

3. Enhancing Animal Welfare: For elephants in captivity, understanding their rumbles can help caretakers improve their welfare by addressing their social and environmental needs more effectively.

Overall, elephant rumbles are a vital aspect of their complex communication system, reflecting the sophistication of their social interactions and the importance of acoustic signals in their daily lives.

Collaboration

This work is a collaboration with The Elephant Listening Project and The Cornell Lab.

To conserve the tropical forests of Africa through acoustic monitoring, sound science, and education, focusing on forest elephants

• The Elephant Listening Project

Fifty microphones are arranged in a grid within the Tropical Forest of Gabon, continuously recording forest sounds around the clock. The provided software is an advanced sound analyzer capable of processing these extensive audio recordings at high speed, allowing for the analysis of terabytes of audio data in just a few days.

Run

Python Code

Once one has followed the setup section below, it is possible to test the rumble detector using the following command:

python ./scripts/model/yolov8/predict_raven.py \
   --input-dir-audio-filepaths ./data/08_artifacts/audio/rumbles/ \
   --output-dir ./data/05_model_output/yolov8/predict/ \
   --model-weights-filepath ./data/08_artifacts/model/rumbles/yolov8/weights/best.pt \
   --verbose \
   --loglevel "info"

Docker Image for Rumble Detector

The Rumble Detector is also available as a Docker image, ensuring portability across different operating systems and setups as long as Docker is installed.

Pull the Docker Image

To pull the Docker image, use the following command:

docker pull earthtoolsmaker/elephantrumbles-detector:latest

Run the Docker Container

To run the Docker container, execute:

docker run --rm earthtoolsmaker/elephantrumbles-detector:latest

Note: By default, audio files and predictions are contained within the container, which limits its practical use. However, this command demonstrates the detector's functionality.

Using Custom Audio Files and Saving Results

To analyze your own audio files and save the results to your machine, you need to mount two directories into the Docker container:

• input-dir-audio_filepaths: The directory containing the audio files to be analyzed.
• output-dir: The directory where the artifacts and predictions will be saved.

In the example below, the input-dir-audio_filepaths is ./data/03_model_input/sounds/rumbles/ and the output-dir is ./runs/predict/. The program will analyze the audio files in the input directory and save the results in the output directory.

docker run --rm \
  -v ./data/03_model_input/sounds/rumbles/:/app/data/08_artifacts/audio/rumbles/ \
  -v ./runs/predict/:/app/data/05_model_output/yolov8/predict \
  earthtoolsmaker/elephantrumbles-detector:latest

Pipeline overview and outputs

The pipeline will do the following:

1. Generate spectrograms in the frequency range 0-250Hz, where all the elephant rumbles are located
2. Run the rumble object detector on batches of spectrograms
3. Save the predictions as a CSV

Note: The verbose flag tells the command to also persist the generated spectrograms and predictions, they will be located in the output-dir.

Spectrogram	Prediction

Below is a sample of a generated CSV file:

probability	freq_start	freq_end	t_start	t_end	audio_filepath	instance_class
0.7848126888275146	185.34618616104126	238.925039768219	6.117525324225426	11.526521265506744	data/08_artifacts/audio/rumbles/sample_0.wav	rumble
0.7789380550384521	187.46885657310486	237.14002966880798	107.4117157459259	112.39507365226746	data/08_artifacts/audio/rumbles/sample_0.wav	rumble
0.6963282823562622	150.82329511642456	238.47350478172302	89.08285737037659	94.3071436882019	data/08_artifacts/audio/rumbles/sample_0.wav	rumble
0.6579649448394775	203.18885147571564	231.6151112318039	44.13426876068115	47.50721764564514	data/08_artifacts/audio/rumbles/sample_0.wav	rumble
...	...	...	...	...	...	...

Benchmark

The aim of this project is to enable the rapid analysis of large-scale audio datasets, potentially reaching terabyte scales. By leveraging multiprocessing and utilizing the maximum number of CPU and GPU cores, we strive to optimize processing speed and efficiency. Benchmark analyses have been conducted on both CPU and GPU to ensure optimal performance.

CPU

Processing a 24-hour audio file on an 8-core CPU takes approximately 35 seconds in total:

• Loading the audio file: ~4 seconds
• Generating spectrograms: ~11 seconds
• Running model inference: ~19 seconds
• Miscellaneous tasks: ~1 second

GPU + CPU

Processing a 24-hour audio file using a GPU (T4) and an 8-core CPU takes approximately 20 seconds in total:

• Loading the audio file: ~4 seconds
• Generating spectrograms: ~11 seconds
• Running model inference: ~4 seconds
• Miscellaneous tasks: ~1 second

Back of the envelope calculation

• Number of sound recorders: $N_{sr} = 50$
• Number of days to analyze: $N_{d} = 30$ (1 month)
• Size of a 24hour audio recording $W = 657$ MB
• Amount of data to analyze: $N_{sr} \times N_{d} \times W = 986$ GB (1 month)
• Time to process a 24h audio file with a CPU: $T_{CPU} = 35$s
• Time to process a 24h audio file with a GPU: $T_{GPU} = 20$s

With CPU

On a CPU setup with 8 cores, analyzing 1 month of sound data - ~1TB - would require: $N_{sr} \times N_{d} \times T_{CPU} = 50 \times 30 \times 35 = 14.6$ hours

To analyze 6 months of sound data - ~6TB - it would require: $N_{sr} \times N_{d} \times T_{CPU} = 50 \times 180 \times 35 = 3.6$ days

With CPU + GPU

On a CPU setup with 8 cores, analyzing 1 month of sound data would require: $N_{sr} \times N_{d} \times T_{GPU} = 50 \times 30 \times 20 = 8.3$ hours

To analyze 6 months of sound data - ~6TB - it would require: $N_{sr} \times N_{d} \times T_{GPU} = 50 \times 180 \times 20 = 2.1$ days

Setup

Dependencies

• Poetry: Python packaging and dependency management - Install it with something like pipx
• Git LFS: Git Large File Storage replaces large files such as jupyter notebooks with text pointers inside Git while storing the file contents on a remote server like github.com
• DVC: Data Version Control - This will get installed automatically
• MLFlow: ML Experiment Tracking - This will get installed automatically

Install

Poetry

Follow the official documentation to install poetry.

Git LFS

Make sure git-lfs is installed on your system.

Run the following command to check:

git lfs install

If not installed, one can install it with the following:

Linux

sudo apt install git-lfs
git-lfs install

Mac

brew install git-lfs
git-lfs install

Windows

Download and run the latest windows installer.

Project Dependencies

Create a virtualenv and install python version with conda - or use a combination of pyenv and venv:

conda create -n pyronear-mlops python=3.12

Activate the virtual environment:

conda activate pyronear-mlops

Install python dependencies

poetry install

Project structure and conventions

The project is organized following mostly the cookie-cutter-datascience guideline.

Data

All the data lives in the data folder and follows some data engineering conventions.

Library Code

The library code is available under the src/forest_elephants_rumble_detection folder.

Notebooks

The notebooks live in the notebooks folder. They are automatically synced to the Git LFS storage. Please follow this convention to name your Notebooks.

<step>-<ghuser>-<description>.ipynb - e.g., 0.3-mateo-visualize-distributions.ipynb.

Scripts

The scripts live in the scripts folder, they are commonly CLI interfaces to the library code.

DVC

DVC is used to track and define data pipelines and make them reproducible. See dvc.yaml.

To get an overview of the pipeline DAG:

dvc dag

To run the full pipeline:

dvc repro

MLFlow

An MLFlow server is running when running ML experiments to track hyperparameters and performances and to streamline model selection.

To start the mlflow UI server, run the following command:

make mlflow_start

To stop the mlflow UI server, run the following command:

make mlflow_stop

To browse the different runs, open your browser and navigate to the URL: http://localhost:5000