I am trying to find the name of a movie. There is this blind boy who recognised a murderer by his whistle.

Can anyone help please.

Thanks

M (1931) - IMDb

"Initially the audience is witness to how particular sound techniques shape this film. For instance, one of the main details that the audience hears is the song that the murderer whistles. Due to the marvel of sound the audience can pick out that the whistling is related to the murderer. Along with the blind man who figured this mystery out, the audience could only put these two together with this sound technique. The director shows the audience how such a simple part of every day sound can be so important to solving such a terrible crime." (The Projector: Film and Media Journal)

No,this does not sound like the film I am looking for.There is a blind young boy not a blind man.