In The Adventure of the Speckled Band what two sounds did Helen hear after she was awakened by her scream?

In "The Adventure of the Speckled Band," Helen Stoner hears two distinct sounds after she is awakened by her own scream:

1. A low, whistling sound: This is described as a "low, whistling sound" that seems to come from the direction of the boarded-up ventilator shaft in her room. This sound is significant because it is the same sound Helen had heard on previous occasions, and it is associated with the danger that is lurking in her room.

2. A heavy, metallic clang: This sound is described as "a heavy, metallic clang," and it seems to come from the direction of her bed. This sound is significant because it seems to be the result of something heavy falling from the ventilator shaft onto her bed.

These two sounds, together with the other details of the story, point to the presence of a dangerous creature that is entering Helen's room through the ventilator shaft.