Q57776: PLAY and SOUND Click Speaker in QuickBASIC; OUT Clicks Less

Article: Q57776
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom SR# S900103-91 | mspl13_basic
Last Modified: 17-JAN-1990

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.

This information applies to Microsoft QuickBASIC Versions 4.00, 4.00b,
and 4.50 for MS-DOS, to Microsoft BASIC Compiler Versions 6.00 and
6.00b for MS-DOS, and to Microsoft BASIC Professional Development
System (PDS) Version 7.00 for MS-DOS.

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

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