ぽそっと

adverb

whispering; murmuring; subdued

Describes speaking in a low, quiet, or subdued voice, often with a sense of hesitation or softness. Onomatopoeic.

• 彼かれはぽそっと「ありがとう」と言いった。

  He murmured a quiet 'thank you'.

• 会かい議ぎ中ちゅう、彼かの女じょはぽそっと意い見けんを述のべた。

  During the meeting, she voiced her opinion in a subdued tone.