How many letters does the top answer for “make a murmuring sound” have?

The most common answer is purl (4 letters).

Crossword clue: make a murmuring sound

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

purl 4 letters wn-def

make a murmuring sound

sough 5 letters wn-def

make a murmuring sound

make a buzzing sound 50% similar → bombinate, buzz

make a crackling sound 50% similar → crackle, crepitate

make a rattling sound 50% similar → brattle, clatter

make a rhythmic sound 50% similar → thrum

make a strident sound 50% similar → blare, blast