At only 28 decibels, the Optoma EH515 has a fairly quiet noise level compared to most of the other 10000:1 contrast ratio projectors that have been available for around the same time as this data projector. The quietest noise level of 10000:1 contrast ratio projectors that were released one year ago is 27dB, the loudest is 48dB, and the average noise level is 34dB.
Alternative 28dB noise level projectors currently available that you might want to consider include the Optoma W515 (£1,807.20) which is cheaper.
If you are not worried about having a louder noise level then you might want to consider the W515T (£1,998) (28dB), or the EH515T (£2,010.40) (28dB) both from Optoma.
What does "noise level" mean?