Sounds beginning at the left part of the mouth (5)
I believe the answer is:
blips
'sounds' is the definition.
(blip can mean an electronic sound)
'beginning at the left part of the mouth' is the wordplay.
'at the left' indicates taking the first letters (the letter on the left end of the word).
'part of the mouth' becomes 'lips' (lips are part of the mouth).
The initial letter of 'beginning' is 'b'.
'b'+'lips'='BLIPS'
(Other definitions for blips that I've seen before include "Small mistakes" , "Glitches" .)