Why are natural sounds collected in Chinese cities?

Noise pollution control is closely related to people's lives. China plans to establish a unified, automatic sound environment quality monitoring network nationwide from January 1, 2025. However, while the automatic monitoring equipment records noise, it will also record nearby bird calls, insect chirps, frog croaks, as well as sounds of wind, rain, and thunder, affecting the evaluation of actual noise conditions.

To help distinguish natural sounds from real noise, the China National Environmental Monitoring Center (CNEMC) has launched the construction of an urban noise measurement database this year. Apart from collecting noise, the work also involves collecting natural sounds in urban areas to enhance the accuracy of noise identification.

Since the first quarter of this year, CNEMC has organized provincial and municipal monitoring stations to conduct natural sound recordings in urban areas in more than 80 cities in China, collecting over 420,000 raw recordings and obtaining more than 80,000 valid recordings. Over 600,000 valid recordings will be collected throughout the year. Based on this data, the largest noise measurement database in the country will be established.

Wang Yun, a senior engineer at the CNEMC, says that after researchers establish this database, the next step is to train and test an intelligent model. In the future, noise monitoring will not only determine whether the noise exceeds the standard, but also identify the source of the excessive noise. For instance, construction noise is a temporary and highly fluctuating noise pollution, which requires special regulation for nighttime construction activities.

While collecting natural sounds and establishing the database, staff at CNEMC also discovered an interesting phenomenon: bird calls, like human speech, are highly diverse. By listening to the sounds, they can identify the species of the birds, determine which area they come from, and even distinguish their state and emotions.