I work as a software developer in an IT service company. Our office has about 50 people. Usually we have our phones on silent mode. Once in a while (approx 1-2 times a month) a phone goes off, since the employee has forgotten to put it on silent mode. Even the amount of time the ringtone we hear is about 2-3 seconds. I don't know why (which I feel) a silly thing like this bothers our manager. One day when a phone went off for 2 seconds, he sent a warning email to office if this repeats again he will disallow phones at work desks. The employee whose phone went off apologized to him replying (all) to his email.
Is this issue so grievous that my manager has to send an email warning to make no phones at work desk? I believe he will do it if it happens and it is bound to happen sometime.
Some background: We do not have any clients visiting our office. Our clients are in US. All our employees are well behaved and nice to each other (even our manager).
Is my manager being unreasonable or it is generally what is adhered in tech companies?