some think active noise cancelling is more harmful to our ears! whats the consensus here?
Why would this be the case, what is the reasoning according to those that make that claim ?
Active noise cancelling reduces the 'seeping through' of constant (low frequency) ambient noises.
This will give a higher attenuation of outside noises and thus one is able to turn the volume down, so you don't have to 'drown out' the outside noises by using a higher volume.
Safer to the ears IMO.
It works by cancellation of sound.
This is how it works:
1 mic is placed OUTSIDE of the ear cup.
1 mic is placed INSIDE of the earcup.
(Topology is a depending on design, manufacturer and type)
The sounds coming from the outside are thus 'known' as the mic picks them up.
The sound inside the ear cup (which is attenuated + changed in frequency spectrum as highs have more 'natural' attenuation.
The music signal is also known (as it is the electrical signal)
When the music signal is 'subtracted' from what's measured by the mic inside the cups the resultant signal is thus the outside noise.
The outside noise is also known and 'filtered' in a similar way as the natural attenuation the cups povide.
This resulting signal is 'inverted' and ADDED to the music signal (in the form of feedabck as used in amplifiers to make them perform better) and thus the outside noises that would (or are) present in the cups are 'cancelled' out acoustically.
The added background hiss is caused by the amplifier section of the measuring mic(s).
Though annoying as it is audibly, it is very low level so not harmful
I think using in ears (I hate them and never use those) will be able to give even higher outside noise attenuation.