# Perl 5: 122 <strike>140</strike> #

No extra libraries. Produces a 1khz 8-bit mono WAV file named 'a':

    open
    A,'>a';print
    A pack"A4lA8lssllssA4ls*",RIFF,17040,WAVEfmt,16,1,1,(1e3)x2,1,8,data,17004,map{($_)x(894261072>>$v++&1?400:100)}(255,0)x20

To get to 122 characters I had to paste the header in binary instead of packing it which makes the code hard to copy here. The escaped version is:

    open
    A,'>a';print
    A"RIFF\x90B\0\0WAVEfmt \0\0\0\0\0\xe8\0\0\xe8\0\0\0\0datalB\0\0",pack"s*",map{($_)x(894261072>>$v++&1?400:100)}(255,0)x20

Base64 encoding of the actual 122 bytes solution:

    b3BlbgpBLCc+YSc7cHJpbnQKQSJSSUZGkEIAAFdBVkVmbXQgEAAAAAEAAQDoAwAA6AMAAAEACABk
    YXRhbEIAACIscGFjayJzKiIsbWFweygkXyl4KDg5NDI2MTA3Mj4+JHYrKyYxPzQwMDoxMDApfSgy
    NTUsMCl4MjA=