weighted decibels (dBA) 20 that aggregate all sound energy in an acoustic scene. Existing technologies are unable to isolate the effect of offending sources, especially in urban environments flooded with multiple sounds. As a result, inspectors resort to long, complicated measurement strategies that often require help from the people responsible for the violation in the first place, an additional factor contributing to the difficulty and reduced efficiency of the enforcement process.

Here, we outline the opportunities
and challenges associated with SONYC,
our cyber-physical systems approach
to the monitoring, analysis, and mit-
igation of urban noise pollution.
Connecting various subfields of com-
puting, including wireless sensor net-
works, machine learning, collaborative
and social computing, and computer
graphics, it creates a potentially
transformative solution to this im-
portant quality-of-life issue affecting
millions of people worldwide. To il-
lustrate this potential, we present
findings from an initial study we con-
ducted in 2017 showing how SONYC
can help understand and address im-
portant gaps in the process of urban
noise mitigation.

SONYC

Multiple research projects have sought
to create technological solutions to
improve the cycle of urban noise pol-
lution. For example, some have used
mobile devices to crowdsource instan-
taneous SPL measurements, noise la-
bels, and subjective responses3, 24, 28 but
generally lag well behind the coverage
in space-time of civic complaint sys-
tems like 311, while the reliability of
their objective measurements suffers
from a lack of adequate calibration.
Others have deployed static-sensing
solutions that are often too costly to
scale up or go beyond the capabilities
of standard noise meters. 4, 23, 29 On the
analytical side, a significant amount of
work has focused on noise maps gener-
ated from sound propagation models
for major urban noise sources (such as
industrial activity and road, rail, and
air traffic). 13, 17 However, these maps
the city, along with citizen reporting,
to fully characterize the phenomenon.

A closely related challenge involves how to respond to potential violations of the noise code. In New York, the subset of noise complaints pertaining to static, systemic sources (such as construction, animals, traffic, air conditioning, and ventilation units) are routed to the city’s Department of Environmental Protection (DEP), which employs approximately 50 highly qualified inspectors to measure sound levels and issue a notice of violation as needed. Unfortunately, the limited human resources and high number of complaints result in average response times of more than five days. Given the ephemeral nature of sound, a very small proportion of inspections actually result in a violation observed, let alone penalized.

To complicate matters, even when noise sources are active during inspections, isolating their individual effect is difficult. Noise is commonly measured in overall sound pressure levels (SPL) expressed in so-called A-

Figure 1. The SONYC cyber-physical system loop, including intelligent sensing, noise analysis at city-scale, and data-driven mitigation. SONYC supports new research in the social sciences and public health while providing the data citizens need to improve their communities.