Is it useful to buy active noise cancelling headphones without playing music?

Morning congestion in the subway noise cancelling earbuds and earphones station, you can always see a good friend with ANC noise-canceling wireless Bluetooth headphones. But there is also a view that if the active noise canceling headphones are worn without music, it is useless. Is this also that?

There are two categories of noise reduction

Sales market above there are many bitmain l7 active noise cancellation headphones, but this wave by AirPodsPro and sonyWH-1000XM4 scraped the real wireless Bluetooth active noise cancellation headphones boom, generally emphasizing the ANC active noise cancellation headphones.
But in fact, noise reduction technology sex to block external noise in these two ways. The first is called passive noise cancellation, and it involves physically blocking out the loud noises in your periphery. The second is called noise reduction, which involves the use of electronics to remove acoustic frequencies before you hear them.

Let's talk specifically about these two methods.

How Passive Noise rapid 3d prototyping Cancellation Works
PassiveNoiseCanceling (PNC) does not apply switching power supplies or electronic systems. Instead, it depends completely on the physics of the natural barrier that protects your ears from the natural environment. Because there is no specific withdrawal of loudness, "noise protection" is the technically appropriate term for cell phone headsets that employ this type of approach.
Most cell phone headsets, especially over-ear and in-ear headsets, have this type of "add-on" effect. They are designed to surround your ears with gaskets (or headphones) to create an airtight seal, which in turn isolates and cuts out natural ambient sound.

Think about what it would sound like if you held your hands over your ears. It's much calmer, isn't it? That's mostly what it does.