The word(s) "soft" appears 2 time(s) in 2 verse(s) in Quran in Muhammad Habib Shakir translation.

(1) On that day they shall follow the inviter, there is no crookedness in him, and the voices shall be low before the Beneficent Allah so that you shall not hear aught but a soft sound.

(سورة طه, Taa-Haa, Chapter #20, Verse #108)
(Arabic, Transliteration, Urdu (Ahmed Ali), Urdu (Jalandhry), Farsi, Yusuf Ali, Shakir, Picthal, Mohsin Khan, French, Spanish, Indonesian, Malay, German, Bosnian, Russian, Dutch, Italian, Portuguese, Tafsir - Jalal ad-Din, Tafsir - King Fahad Quran Complex)

(2) O wives of the Prophet! you are not like any other of the women; If you will be on your guard, then be not soft in (your) speech, lest he in whose heart is a disease yearn; and speak a good word.

(سورة الأحزاب, Al-Ahzaab, Chapter #33, Verse #32)
(Arabic, Transliteration, Urdu (Ahmed Ali), Urdu (Jalandhry), Farsi, Yusuf Ali, Shakir, Picthal, Mohsin Khan, French, Spanish, Indonesian, Malay, German, Bosnian, Russian, Dutch, Italian, Portuguese, Tafsir - Jalal ad-Din, Tafsir - King Fahad Quran Complex)