To drive this point home, here is the low-frequency spectrum of a popular Hip Hop song The white noise would have become so loud at other frequencies that it would be disturbing and likely detrimental to our hearing. We would have to raise the sound level of the machine by more than 20 decibels to have any hope of drowning out the footfalls, but the machine is already running at 90% volume.īut even if we could increase the volume to completely cover the footstep noise the result wouldn’t be good: That is merely a drop in the bucket when it comes to masking this stomping noise. So -20 decibels at 40 Hz, means at 40 Hz, the white noise is only 25% as loud as the footsteps.
Roughly speaking, -10 decibels is being perceived as half as loud. But it is louder at higher frequencies only!Īt 90 Hz, the white noise machine’s sound level is already 10 decibels lower.Īt 40 Hz-the frequency of the max footfall sound level-the white noise machine’s output is more than 20 decibels lower. Note: Because of our hearing is more sensitive at 125 Hz than at 40 Hz, the white noise machine will even appear louder than the stomping noise. The white noise sound level at around 125 Hz is about the same as the footfall’s maximum sound level, but unfortunately it is at a much higher frequency. Note how the area (below 100 Hz) where most of the footfall’s sound energy lies is mostly white. Now let’s look at the lowest-pitched white noise (dark-brown noise) of one of the largest white noise machines on the market: The footfall’s max sound level is at around 40 Hz, but there is substantial energy between 20 and 70 Hz. Take a look at the dominant frequencies in a footfall caused by someone walking on a wooden floor, recorded in the downstairs apartment Note: Additionally, because the speaker cannot reproduce low frequencies well, many manufacturers filter (roll-off) the low-frequencies from their white noise to prevent distortions. The speaker of most white noise machines cannot reproduce the low frequencies that are disturbing in low-frequency noise intruders (e.g., bass-heavy music, footfalls, rumbling), or at least it cannot produce them loud enough.Īs a result you’ll hear loud white noise and you’ll hear the neighbor’s footfalls or subwoofer. With low-frequency noise, the problem most often is point number two: It needs to contain the frequencies of the noise intruder, or at least be relatively close.It needs to be louder than the noise intruder.To use white noise (masking noise) to drown out (mask) intermittent disturbing noises (noise intruders), the masking noise needs to have two characteristics: Why does your white noise machine not mask low-frequency noise Perhaps your machine was even set a lot louder than the noise you were trying to block. Now you are wondering what is going wrong. Or perhaps you tried to cover an obnoxious hum permeating your room.Īlas, the white noise machine didn’t help all that much. You have been running your white noise machine at maximum volume to drown out the stomping from above, the neighbor’s bass-heavy music, or the rumbling of the trucks passing by.
0 kommentar(er)
