Methods of analysis for urban environmental noise

Acoustic pollution in the past is insignificant when compared with urban environmental noise today. The control of environmental noise, in comparison to other pollutants, had been hampered by insufficient knowledge of its effects on humans. This work presents several results about the urban acoustic impact. The experimental place is the Historical Centre of Mexico City. A distributed wireless monitoring system was developed and installed. Each node includes a half-inch pre-polarized IEC 61672 Class 1 microphone mounted 4m above the road surface in a weatherproof case, a dynamic range data acquisition card, an industrial computer and wireless connection to Internet by means of a 3G Mobile Broadband. The noise level measurements at each point are made every 30 seconds, at 25 Ks/s and 24-bit resolution analogue-to-digital conversion (ADC), and the data sent to the main monitoring station every five minutes. Additionally, this paper presents a neural recognition model of five dominant environment noise sources in the measured signal mixture which is common in some critical points in urban areas.