Συντελεστης ηχοαποροφησης

[dervast]

Καλησπερα ο συντελεστης ηχοαπορροφησης, π.χ

αw=0,70

σημαινει οτι το υλικο εξασθενει ολες τις συχνοτητες το ιδιο;

Ευχαριστώ
Αλέξανδρος

 

[gorg]

Ο συντελεστής ηχοαπορρόφησης a εξαρτάται από την συχνότητα, αλλά ο a_w, σύμφωνα με το ISO 11654, είναι σταθμισμένος (weighted) και ανεξάρτητος.

 

[gorg]

Παραθέτω από κάπου:

Noise Reduction Coefficient (NRC) is the average of how much of the sound that hits the surface of material that is absorbed on 4 specific frequencies. These frequencies are 250 Hz, 500 Hz, 1000 Hz and 2000 Hz. The reason for choosing these particular frequencies is that they are located within the frequency range of human speech and it would be easy to assume that they should be more important to monitor compared to other frequencies of sound above or below these.

Just like the NRC, the weight alpha is a calculated average of the material’s ability to absorb sound in a range of frequencies. While NRC is the arithmetic average of the absorption in four specific frequencies, in ISO 1654 the practical absorption is calculated in the octave bands 250 hz, 500 hz, 1000 hz, 2000 hz and 4000 hz. The practical absorption coefficient is the arithmetic average of the 1/3 octave bands having each and one of those octave band frequencies as their centre frequency. The practical absorption coefficients in the given octave bands are then compared with a set of reference curves in steps of 0.05 where the maximum negative sum of deviations must not exceed 0.10. The weighted alpha is then the reference curve absorption at 500 Hz.