The Egyptian government has proposed unifying the call to prayer in Cairo by introducing a single call delivered by a radio network.
Cairo prayer calls are transmitted via loudspeakers
Religious affairs minister Mahmoud Hamdi Zaqzouq said there should be "one live voice" broadcast simultaneously from Cairo's 4,000 mosques.
However, some Muslims have opposed the suggestion, with one Islamic web site saying it amounted to "treason".
With 16 million residents, Cairo is the Muslim world's most populous capital.
Prayer calls are transmitted via loudspeakers of mosques five times a day.
Mosques often announce the prayers two or three minutes apart, causing much confusion.
"Everyday I receive complaints from people about the loudspeakers and when I ask them to make official
complaints, they say they were afraid of being accused of being infidels or acting against religion," Mr Zaqzouq said.
Following opposition to the plan on Web sites and in newspapers, he said he did "not expect this fuss... as if it was a doomsday".
"In fact, the loudspeakers are heresy because Islam has been doing fine for 1,350 years
without loudspeakers," he said.
He said muezzins, who deliver the prayer call, would not be out of a job, as they could re-train as imams, which are currently in short supply.
Two of Egypt's top clerics have said the initiative does not contravene Islamic law.
"It is religiously legitimate... that the city has one prayer call," Grand Mufti Ali Gomoa said in a statement.
He pointed out that some countries, such as Turkey, have unified the prayer call in each city.
"We have a kind of disorganisation and contradictions in
the voices of the prayer callers that hurt the sentiments
of the Muslims," former Mufti Nasser Farid Wassel wrote in al-Lewaa al-Islami newspaper, which is
published by the ruling National Democratic Party.
The government has said the plan may be implemented in other cities in Egypt.