[kazinator]

-12 dB is 94%. 12 decibels is 1.2 bels.

10^(-1.2) = 0.063 so 12 dB down means intensity is reduced to 6.3%, or by 93.7%.

-12 dB is a worthwhile cut if it can be achieved with a barrier that has some good qualities: being unobtrusive, reasonably light-weight, thin, cost effective, perhaps transparent or translucent, etc.

If you double it up, -24 dB may be possible.

Stopping sounds in higher frequency ranges has applications. It won't block your neighbor's thumping bass, but there are other situations that benefit from noise blocking, like appliances with motors.