Now Hear This

If by “downtown New York City” you mean areas such as Lower Manhattan, the Financial District, Tribeca, and surrounding streets, the average ambient sound pressure level is typically about 70–75 dBA (A-weighted decibels) during daytime street activity.  

For context:

Environment

Typical Sound Level

Quiet suburban neighborhood

40–50 dBA

Normal conversation

60–65 dBA

Downtown Manhattan street

70–75 dBA

Heavy Midtown traffic

70–85 dBA

Motorcycle

~88 dBA

NYC subway platform

~94 dBA average

Jackhammer

~110 dBA

A large NYC street-noise study found an average street-level noise exposure of 73.4 dBA, with measurements ranging from about 56 dBA to 95 dBA depending on location, traffic, construction, and time of day.  

For comparison to motorcycle riding:

• Downtown Manhattan at 73 dBA is roughly 1/100th the acoustic energy of a 93 dBA environment.
• Every 10 dB increase represents about 10× more sound energy.
• Typical motorcycle helmet noise at freeway speeds is often 90–105 dBA, substantially louder than standing on a downtown NYC sidewalk.  

Given your interest in motorcycle hearing protection, a downtown Manhattan street is generally similar to riding a motorcycle at very low speed with a good helmet and windshield, while freeway riding is dramatically louder.