Whistles
there own voices :O
The men with whistles are Referees they look out for fouls, penalties , etc. There are usually 2 Refs.
Any standard whistle used by referees in any other sport will work.
it was formally introduced in 1870 but was used since 1840 in th UK
In American sports, the referees usually wear black and white striped shirts. In the NBA, the officials wear grey shirts.
Usually, in higher class games (i.e. NBA, NCAA, etc.) there are three. In tourney games, there are three. In high school games and junior high games, there are most likely two.15 total2 sometimes 1
The official number of referees in an NBA game or collegiate basketball is 3. The referees are the officers in charge of a basketball game and the final decision lies within their power.
Aluminum
The League pays the salaries of the referees who work games in the NFL. The NFL Officials Union and the NFL agreed to an 8 year contract in 2012. The deal, the longest ever between the league and union, was brokered after the Refs went on strike and refused to work games in the 2012 season.
$10 for sideline referees and $15 for the center referee per game. That is how much they usually get paid. This is a vague answer. How much you get paid depends on your organization. The higher age group you do the more you get paid.
In some religions whistles are made from the stalks of the horsetail. They make these whistles to call the spirits.