High decibels and damage to hearing
Musicians are known to get hearing damage (eg hearing loss, tinnitus) in the long term from playing in loud gigs and concerts, and even the violin on its own is quite capable of generating 100dB only a few inches under its player’s left ear.
If anyone has concerns about possible damage to hearing from excessive exposure to sound at a high decibel level there is available for the iPhone and iPad an inexpensive, accurate and very well provided decibel meter app SPLnFFT. I don’t know if it is available on Android phones.
SPLnFFT displays on-screen live decibel measurements in the range 20-130 dB derived from sound signals received by the device. There is also a real time "thermometer" scale detailing the possible effects of various decibel levels from 20-120:
20 Almost silent
30 Very quiet
70 Loud - possible annoyance
80 Too loud - exposure time limited
90 Very noisy - exposure time < 2h 30min
100 Very noisy - exposure time < 15 min
110 Extremely noisy - exposure time < 1min
and, provided by me,
130 You do not want to go there if you value your life!
In any listening session the app displays not only the live dB reading but also the instantaneous minimum, maximum, and various kinds of statistical averages ("Leq" is probably the most generally useful one). The app also provides a window displaying graphically in real time the frequencies currently being received. There are many other technical features that I have yet to explore.
The FFT in the app’s name refers to "Fast Fourier Transform", an advanced mathematical method for breaking down a sound or any other signal into its constituent frequencies so that they can be displayed on screen.
I’ve tried out the app with my two violins and an iPad about 3 feet away (just try holding an iPad up by one’s left ear while playing the violin!), and by playing strongly over the whole range of the instrument I obtained, depending on which fiddle I was using, dB readings of 86-89 dB without a mute, 83-87 dB with an orchestral mute, and 75-80dB with a heavy practice mute. However, these readings were for the sound received by the iPad 3 feet away, and because of the inverse square law non-muted sounds would be equivalent to 90-100 dB or so under my left ear.
For some time now I’ve been using a cotton wool plug in my left ear when playing in many music ensembles (in particular symphony orchestras, anything with PA, and some sessions), and the results I have from the above tests do not persuade me otherwise. Playing with a plug in my left ear in those circumstances actually helps me not only to hear my own intonation better but also the fine detail of what is going on around me.