What are the problems with calculating the speed of a sound wave by dividing the distance travelled by the time taken?

The problem with calculating the speed of a sound wave by dividing the distance travelled by the time taken, is every person has a different reaction time. This causes random errors but can be resolved a larger group making new measurements. These results would then be used to calculate a new mean. Another problem is that the time between hearing the cymbals and seeing them clash is very short, making it difficult to press the timer at the right time. This may be solved by increasing the distance between person A and B, as a greater distance will give a greater waiting period to hear the cymbals clash.