Noise affects people in a variety of ways. It can cause annoyance, sleep disturbance or hearing damage.
With annoyance, the measured level of noise is only one factor in this. The character of the noise, the context in which it is heard and factors unrelated to acoustics may all play a part.
I can advise developers, councils or residents on how a noise source is likley to affect people round about or I can help those affected by existing noise to decide whether they have a case for nuisance.