Trumpets can generate levels in excess of 110 dB SPL (usually less than 120 dB SPL). The actual output can be affected by many factors, including mouthpiece, type of trumpet, sub-glottal (or blowing) pressure of the trumpet player, and also where the sound is measured. If you measure at a point directly in front of a trumpet, this will give you the highest possible measure-especially for the mid- and higher frequencies. However, if you measure at the point of the trumpet players ear, the intensity is significantly lower. This is because the higher frequency components of the trumpet are very directional- almost like a laser beam. The intense high-frequency components view the trumpet like a wave guide and results in this high frequency, intense energy going away from the trumpet player. As a result, the trumpet player is in a safe position (unless there is another trumpet player to his rear). This is one reason why trumpet players should be placed on risers- the intense high-frequency energy literally goes over the heads of those other musicians downwind.
The human auditory system is very robust. It can stand very intense music and noise levels over short periods of time with little or no damage. The typical output of a trumpet player, if sustained over a long period of time (in conjunction with other musical instruments in the band or orchestra), can be damaging. The damage however, will be gradual and tend to affect the 3000-6000 Hz region first, and will not cause a person to ''become deaf''. Research suggests that the human ear can only tolerate 80 dB (A-weighted) without hearing damage. Levels of 85 dB A or greater will cause damage but it also depends on the duration of the exposure. A playing level of 85 dBA can be withstood for about 30-40 hours per week of playing with no measurable damage. This maximum weekly exposure however drops to about half that time for every 3 decibels of increase in playing level. For example, if one is exposed to a constant 100 dBA sound, one should only be in that environment for about 1 or 2 hours each week.
Understandably, musicians should be wearing hearing protection and there are excellent types that treat all of the music sound uniformly such that music still sounds like music.