61.  And utter not thy prayer aloud, nor utter it too low, but seek a way between

[17:111] Say, ‘Call upon Allah or call upon Rahman; by whichever name you call Him, His are the most beautiful names.’ And utter not thy prayer aloud, nor utter it too low, but seek a way between.

[20:109] On that day they will follow the Caller straight, there being no deviation therefrom; and all voices shall be hushed before the Gracious God and thou shalt not hear but a subdued sound of footsteps.

[20:8] And if thou speakest aloud, it makes no difference, for He knows the secret thought and what is yet more hidden.

Courtesy Amjad Tariq, Sydney