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NR NC Rw Ctr STC Lnw

The button NR curve inserts two functions. The function NRRate finds the corresponding NR curve for the row above. The function NRCurve returns the values of the curve at each octave band.

Function NR_rate(DataTable As Variant, Optional fstr As String)

NR curves are defined in AS1469:1983 Acoustics - Methods for the determination of noise rating numbers. The standard includes a method for comparing a given sound spectrum to the set of curves and returning the corresponding curve.

-	31.5	63	125	250	500	1k	2k	4k	8k
A_f	55.4	35.5	22	12	4.8	0	-3.5	-6.1	-8
B_f	0.681	0.79	0.87	0.93	0.974	1	1.015	1.025	1.03

The values of a given NR curve at each frequency is given by:

NRcurve = A_f+(B_f*Curve_no)

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Function NRcurve(Curve_no As Integer, fstr As String)

Some applications for various NR curves are:

Rating	Application
NR 25	Concert halls, broadcasting and recording studios, churches
NR 30	Private dwellings, hospitals, theatres, cinemas, conference rooms
NR 35	Libraries, museums, court rooms, schools, hospitals, hotels, executive offices
NR 40	Halls, corridors, restaurants, night clubs, offices, shops
NR 45	Department stores, supermarkets, canteens, general offices
NR 50	Typing pools, offices with business machines
NR 55	Light engineering works
NR 60	Foundries, heavy engineering works

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Function NCcurve(Curve_no As Integer, fstr As String)

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The button 'Rw Curve' inserts two functions. The function RwRate finds the corresponding Rw curve for the row above. The function RwCurve returns the values of the curve at each octave or one-third-octave band.

Function RwCurve(CurveNo As Variant, fstr As String)

R_w is a rating curve defined in ISO717.1 - Acoustics - Rating of sound insulation in buildings and of building elements -- Part 1: Airborne sound insulation. The standard defines a family of curves of the same shape and the rules for rating a given set of transmission loss data against the set of curves.

Reference curve (Rw52)	100	125	160	200	250	315	400	500	630	800	1k	1.25k	1.6k	2k	2.5k	3.15k
1/3 Octave Band	33	36	39	42	45	48	51	52	53	54	55	56	56	56	56	56
Octave Band		36			45			52			55			56

The name/value of a particular curve is given by the value at the 500Hz band.

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Function RwRate(DataTable As Variant, Optional Mode As String)

ISO717.1 requires that the corresponding curve have a sum of deficiencies less than:

• 32 dB (in one third octave bands) or
• 10 dB (in octave bands)

The function adds each band that is below the curve to SumDeficiencies. If the result is less than the allowable sum of deficiencies, the curve is moved up by 1dB and the process loops. Once the maximum allowable sum of deficiencies is exceeded, the curve is moved down 1dB (as this sum of deficiencies is not allowed).

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Function CtrRate(DataTable As Variant, rw As Integer)

C_tr is a correction for the spectral characteristics of traffic noise. The function uses the spectral adaptation terms from ISO717.1 - Acoustics - Rating of sound insulation in buildings and of building elements -- Part 1: Airborne sound insulation.

Reference Curve	100	125	160	200	250	315	400	500	630	800	1k	1.25k	1.6k	2k	2.5k	3.15k
1/3 Octave Band	-20	-20	-18	-16	-15	-14	-13	-12	-11	-9	-8	-9	-10	-11	-13	-15
Octave Band		-14			-10			-7			-4			-6

The function logarithmically subtracts the input Transmission Loss Spectrum DataTable from the reference spectrum shown in the table above.

X_A_ji = -10*log(10^((L_ij - X_1)/10)))

The final C_tr value is the difference between this value and the single number value (R_w, R'_w D_nTw etc...).

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The button 'STC Curve' inserts two functions. The function STCRate finds the corresponding Rw curve for the row above. The function STCCurve returns the values of the curve at each one-third-octave band.

Function STCCurve(CurveNo As Variant, fstr As String)

STC (Sound Transmission Class) is system of rating curves defined in ASTM E413 - 2016 Classification for Rating Sound Insulation. The standard defines a family of curves of the same shape and the rules for rating a given set of transmission loss data against the set of curves. The Sound Transmission Class is typically used for partition systems tested in the USA. The rating standard only considers frequencies from 125Hz to 4kHz bands - see ISO standard.

Reference curve (Rw52)	125	160	200	250	315	400	500	630	800	1k	1.25k	1.6k	2k	2.5k	3.15k	4k
1/3 Octave Band	36	39	42	45	48	51	52	53	54	55	56	56	56	56	56	56

The name/value of a particular curve is given by the value at the 500Hz band.

Function STCRate(DataTable As Variant, Optional Mode As String)

The function identifies the STC curve that matches the input spectrum. The identified curve is the highest STC curve that has:

• Sum of deficiencies less than 32 dB AND
• maximum deficiency in any one-third-octave band is less than 8dB

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The button 'Lnw Curve' inserts two functions. The function LnwRate finds the corresponding Lnw curve for the row above. The function LnwCurve returns the values of the curve at each octave or one-third-octave band.

The L_nw rating curve is defined in ISO717.2 Acoustics - Rating of sound insulation in buildings and of building elements -- Part 2: Impact sound insulation. The standard defines a family of curves of the same shape, and the rules for rating a given set of impact sound measurements against the set of curves.

Function LnwCurve(CurveNo As Variant, fstr As String) 'Optional Mode As String)

Reference Curve Lnw60	100	125	160	200	250	315	400	500	630	800	1k	1.25k	1.6k	2k	2.5k	3.15k
1/3 Octave Band	62	62	62	62	62	62	61	60	59	58	57	54	51	48	45	42
Octave Band		62			62			60			57			48

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Function LnwRate(DataTable As Variant)

ISO717.2 requires that the corresponding curve have a sum of deficiencies less than:

• 32 dB (in one third octave bands) or
• 10 dB (in octave bands)

The function adds each band that is below the curve to SumDeficiencies. If the result is less than the allowable sum of deficiencies, the curve is moved down by 1dB and the process loops. Once the maximum allowable sum of deficiencies is exceeded, the curve is moved up 1dB (as this sum of deficiencies is not allowed).

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