Tuning Fork

Remember the SOUND statement (last heard from in chapter 9):

SOUND frequency,duration

In this statement,

• frequency —— is the frequency of the sound in vibrations per second (sometimes called hertz.) It must be more than 37 and less than 32,000 or so.
• duration —— is the length of time to play the sound in clock "ticks". There are about 18 ticks per second.

Here is a program (which you have seen before) which asks the user for a frequency, and then plays that frequency for about one second.

' Tuning Fork Program
'
PRINT "Enter the frequency (37-32000):"
INPUT FREQ
SOUND FREQ, 18
END

The program expects the user to enter a correct frequency value. If the user does not, the SOUND statement will not work. A better program tests FREQ before executing the SOUND statement:

' Tuning Fork Program
'
PRINT "Enter the frequency (37-32000):"
INPUT FREQ
IF ____________ AND _____________ THEN
  SOUND FREQ, 18
ELSE
  PRINT "Frequency is out of range"
END IF
'
END