Results in noise research produced during the last 10 years confirmed that annoyance and loudness are two closely related values, the rating of which differs only in rare cases. This finding is helpful in judging the efficiency of noise reduction steps and in fighting noise pollution. Loudness calculation procedures which produce values in close agreement with human sensations can be used either as computer programs or as loudness meters. Two examples for the use of loudness in assessing everyday problems are given. The two examples are transmission loss and addition of noise sources.