PLAY and SOUND Click Speaker in QuickBasic; OUT Clicks Less (57776)

SUMMARY

In QuickBasic, the PLAY and SOUND statements produce a click on the speaker noticeable at the end of a sound. Also, if an inaudible frequency is used with the SOUND statement, a click is heard before and after the PLAY or SOUND statement.

This article shows a method using the OUT statement to produce sounds where the clicking is less noticeable.

MORE INFORMATION

The following program produces the clicking noise and then shows an improvement involving programming the timer chip as explained in the following book:

"The New Peter Norton Programmer's Guide to the IBM PC & PS/2," by Peter Norton and Richard Wilton (Microsoft Press, 1988). Pages 148-150.

Code Example

' The following PLAY statement demonstrates the clicking sound:
FOR i% = 1 TO 3
  PLAY "L4 C"
  SLEEP 1
NEXT
' The following SOUND statement demonstrates the clicking sound:
FOR i% = 1 TO 3
  SOUND 700, 12
  SLEEP 1
NEXT
' The following OUT statements alleviate the clicking sound while
' generating tones:
count1 = 1193280! / 700        ' 700 is the desired frequency
count2 = 1193280! / 100000     ' 100,000 is the desired inaudible frequency
lo.count1 = count1 MOD 256     ' calculate low-order byte values
lo.count2 = count2 MOD 256
hi.count1 = count1 / 256       ' calculate high-order byte values
hi.count2 = count2 / 256
OUT &H43, &HB6                 ' get timer ready
old.port = INP(&H61)           ' read the value at port 61H
new.port = (old.port OR &H3)   ' set bits 0 and 1
OUT &H61, new.port             ' turn speaker on
FOR i% = 1 TO 3
  OUT &H42, lo.count1          ' load low-order byte for first frequency
  OUT &H42, hi.count1          ' load high-order byte for first frequency
  SLEEP 1
  OUT &H42, lo.count2          ' load low-order byte for second frequency
  OUT &H42, hi.count2          ' load high-order byte for second frequency
  SLEEP 1
NEXT
OUT &H61, old.port             ' turn speaker off
END