The phrase "subtle sound" is correct and usable in written English.
You can use it to describe a sound that is quiet, soft, and unclear. For example, "The night was still, broken only by a subtle sound in the distance."
(He also created the wonderfully subtle sound design).
His labor has an almost musical quality, enhanced by Mr. Benicheti's sharp and subtle sound design.
A once multi-faceted, subtle sound has had all its hues ramped up to neon.
Although berries and beans may be separated by a subtle sound within a language, the larger space between like words in different languages is just as hazardous.
"And there's a lot of Web use in open air workplace environments, so we're looking for a more subtle sound experience".
Each must the other take not for his high, / His puissant front nor for her subtle sound, / The shoo-shoo-shoo of secret cymbals round".
And in many areas of the parks, the roar of traffic drowns out the subtle sounds of nature.
There have been some suggestions that breaches are some form of acoustic signal, used more frequently on windy days when surface chop drowns out more subtle sounds.
By staving off hearing damage later in life, listeners will still be able to hear subtle sounds, like fingers on frets or page-turning.
Moreover, research suggests that people with misophonia have a higher amount of myelination in their medial frontal cortex, which may potentially be responsible for the hyperactive sensitivity they experience from what the average person would deem to be subtle sounds.
Most of the earbuds distributed with MP3 players are passable at best, with little ability to replicate deep bass tones, and only average clarity in accurately reproducing subtle sounds such as cymbal brushes or acoustic instruments.
