By night, he’s a DJ, spinning heavy metal in East Village clubs. By day he measures noise pollution.


In a city where noise is the perennial No. 1 complaint to 311, headbanger Benjamin Sachwald helped the rewrite the noise code.


The firm he works for, AKRF, updated the sound standards for the 21st century, adding requirements for Mister Softee trucks. The company also does readings for fed-up tenants living above bars and developers planning projects by elevated subways.


As a drummer for heavy metal bands — his last was called Take This City by Nightfall — Sachwald is sensitive to being a noise-maker. “I don’t practice in my apartment,” he said. “People don’t want to hear their neighbors.”


Sachwald demonstrated the barrage beneath the N/W tracks at 39th Avenue in Queens a couple of weeks ago — a “fairly noisy” 82 decibels. As a state authority the MTA isn’t subject to city codes. But the agency does plan to issue recommendations by January for reducing subway clamor.

“Studies show exposure to noise can lead to certain health problems like high blood pressure, stress, anxiety,” he said. “What’s really unpleasant is when you get that metal-on-metal screeching. I hear that and start thinking of the appropriate way to mitigate it.”