This is the 14920th most frequent German word.
ruhige
Calm; quiet.
Here, 'ruhige' modifies 'Atmosphäre' (feminine singular noun), indicating peace or calm.
Er liebt diese ruhige Atmosphäre.
He loves this calm atmosphere.
In this case, 'ruhige' characterizes 'Stimme' (feminine singular noun), describing its gentle and calming quality.
Die ruhige Stimme beruhigt alle.
The calm voice soothes everyone.
The word 'ruhigen' is the accusative singular feminine form of 'ruhig,' describing the street ('Straße') in the sentence.