IEVref: 801-22-13 ID: Language: en Status: Standard Term: spectrum density level Synonym1: spectrum level [Preferred] Synonym2: Synonym3: Symbol: Definition: level of the limit, as the width of the band approaches zero, of the ratio of a specified quantity distributed within a frequency band to the width of the band NOTE 1 – The kind of quantity must be specified, such as by (squared) sound pressure spectrum level. NOTE 2 – In view of the fact that filters have finite bandwidths, practically the sound pressure spectrum level Lps is obtained for the centre frequency of the band by the formula: ${L}_{\text{ps}}=10\text{\hspace{0.17em}}\text{\hspace{0.17em}}{\text{log}}_{10}\frac{\left({p}^{2}/B\right)}{\left({p}_{0}^{2}/{B}_{0}\right)}\text{\hspace{0.17em}}\text{dB}$ where p and p0 are respectively the given field quantity and the reference quantity; B et B0 are respectively the effective bandwidth of the filter and the reference bandwidth of 1 Hz. When Lp is the band pressure level observed through the filter, the above relation reduces to ${L}_{\text{ps}}={L}_{\text{p}}-{\text{log}}_{10}\left(B/{B}_{0}\right)\text{\hspace{0.17em}}\text{dB}$ Publication date: 1994-07 Source: Replaces: Internal notes: 2017-06-02: Cleanup - Remove Attached Image 801-22-131.gif 2017-06-02: Cleanup - Remove Attached Image 801-22-132.gif CO remarks: TC/SC remarks: VT remarks: Domain1: Domain2: Domain3: Domain4: Domain5: