Rating of sound insulation in buildings and building elements, Part 1: Airborne sound insulation in buildings and of interior building elements

IS 11050 Part 1: Scope - Key Formulas, Tables & Specifications

1. Scope Summary

• Defines single-number quantities for airborne sound insulation of building elements.
• Reference values for comparison are given in Table 3.
• Measurement results (R, R', Dw, DnT,w) are compared against reference curves shifted in 1 dB steps.
• The weighted index (Rw, R'w, Dw, DnT,w) is the reference curve level at 500 Hz after shifting.
• Maximum unfavourable deviation > 8 dB must be reported.

2. Key Tables

| Table 1: Single-number quantities (interior elements) | |----------------|---------|-----------------------------|-------|---------|---------| | Weighted sound reduction index | Rw | Sound reduction index (K) | ISO 140-3 | Formula (3) | | Weighted apparent sound reduction index | R' | Apparent sound reduction index (R') | ISO 140-4 | Formula (5), (6) |

| Table 2: Single-number quantities (between rooms) | |----------------|---------|-----------------------------|-------|---------|---------| | Weighted-level difference | Dw | Level difference (D) | ISO 140-4 | Formula (2) | | Weighted standardized level difference | DnT,w | Standardized level difference (DAT) | ISO 140-4 | Formula (3) |

| Table 3: Reference values for airborne sound (dB) |

3.

IS 11050 Part 1: Key Terms, Definitions, and Specifications

1. Method of Comparison (Clause 4.3)

• Shift the reference curve (Table 3 values) in 1 dB steps toward the measured curve.
• Calculate mean unfavourable deviation (only where measured < reference).
• Stop when mean deviation ≤ 2.0 dB and as large as possible.
• Record Rw, R'w, Dw, DnTw at 500 Hz after shifting.
• Report max unfavourable deviation if > 8.0 dB.

2. Single-Number Quantities (Tables 1 & 2)

3. Reference Values for Airborne Sound (Table 3)

Summary Diagram: Method of Comparison

flowchart TD
    A[Measured Curve] --> B[Reference Curve]
   

IS 11050 Part 1: Single-number Quantities for Airborne Sound Insulation Rating

Key Definitions (Clause 3.1 & Tables)

• Single-number quantity: Value in dB of the reference curve at 500 Hz after shifting per ISO 717.
• Symbols & Types:

Reference Curve Values (Table 3)

Evaluation Procedure (Clause 4.3)

• Shift the reference curve in 1 dB steps towards the measured one.
• Calculate mean unfavourable deviation (only frequencies where measured < reference).
• Stop shifting when mean unfavourable deviation ≤ 2 dB and as large as possible.
• The shifted reference value at 500 Hz = Rw, R'w, Dw, or DnT,w.
• Record max unfavourable deviation if > 8 dB.

Margin Calculation (Clause 3.2)

[ \boxed{ \begin{aligned

IS 11050 Part 1: Reference Values for Airborne Sound Insulation

Key Reference Values (Table 3)

Method of Comparison (Clause 4.3)

• Shift the reference curve in 1 dB steps towards the measured curve.
• Calculate mean unfavourable deviation (only when measured < reference).
• Mean deviation ≤ 2.0 dB, maximize this value.
• Record maximum unfavourable deviation if > 8.0 dB.
• The shifted reference value at 500 Hz is the single-number rating (Rw, R'w, Dw, or DnT,w).

Single-Number Quantities (Tables 1 & 2)

Summary Diagram (Conceptual)

graph LR
A[Measured Sound Reduction] --> B[Compare with Reference Curve]
B --> C{Shift Reference Curve by 1 dB steps}
C --> D[Calculate Mean

IS 11050 Part 1 — Method of Comparison for Airborne Sound Insulation

Key Specifications & Procedure (Clause 4.3):

• Measurement results (R, R', Dw, DnT) are taken in one-third octave bands (100 Hz to 3150 Hz).
• The reference curve (Table 3 values) is shifted in 1 dB steps towards the measured curve.
• Calculate mean unfavourable deviation = sum of deviations where measured < reference, divided by 16 frequencies.
• Shift until mean unfavourable deviation is maximized but ≤ 2.0 dB.
• The value of the shifted reference curve at 500 Hz is the single-number rating (Rw, R', Dw, or DnT,w).
• Record the maximum unfavourable deviation if > 8 dB.

Reference Values (Table 3):

Summary of Method:

flowchart TD
    A[Measured one-third octave band values] --> B[Compare with Reference Curve]
    B --> C{Shift reference curve in 1 dB steps}
    C --> D[Calculate mean unfavourable deviation]
    D --> E{Is mean deviation ≤ 2 dB & max?}
    E -- Yes --> F[Determine Rw, R', Dw, or DnT,w at 500 Hz]
    E -- No --> C
    F --> G[Report results including max unfavourable deviation if > 8 dB]

Important Notes:

• Use **one decimal

IS 11050 Part 1: Procedure for Evaluating Single-number Quantities

1. Method of Comparison (Clause 4.3)

• Shift the reference curve (Table 3 values) in 1 dB steps towards the measured one-third octave band values.
• Calculate mean unfavourable deviation = sum of deviations where measured < reference / 16 frequencies.
• Shift until mean unfavourable deviation is maximized but ≤ 2.0 dB.
• Record the value at 500 Hz after shifting as the single-number quantity (Rw, R'w, Dw, or DnT,w).
• Record maximum unfavourable deviation if > 8 dB.

2. Reference Values (Table 3)

3. Single-number Quantities

4. **Margins (Clause

Statement of Results - IS 11050 Part 1 (Based on ISO 717/1)

Key points:

• Reference curve shifting (Clause 4.3):
  Shift the reference curve in 1 dB steps towards measured values to maximize the mean unfavourable deviation ≤ 2.0 dB (only deviations where measured < reference count).

  • Mean unfavourable deviation:
    [ \text{Mean deviation} = \frac{\sum \text{unfavourable deviations}}{16} ]
  • The value at 500 Hz after shifting = Rw, R'w, Dw, or DnT,w.

• Maximum unfavourable deviation:
  Report if > 8.0 dB.

• Single-number quantities (Tables 1 & 2):

  Quantity	Symbol	Derived from band values	ISO 140 Part	Formula Ref.
  Weighted sound reduction index	Rw	Sound reduction index K	3.1	(3)
  Weighted apparent sound reduction index	R'	Apparent sound reduction index R'	3.4	(5),(6)
  Weighted level difference	Dw	Level difference D	4	(2)
  Weighted standardized level difference	DnT,w	Standardized level difference DAT	4	(3)

• Margin (Clause 3.2):
  [ M_a = R_w - 52 \text{ dB} \quad;\quad M'_a = R'_w - 52 \text{ dB} ]

• Reference values for airborne sound (Table 3):
  Frequency (Hz) → Reference value (dB)
  100 → 33, 125 → 36, ..., 500 → 52, ..., 3150 → 56 (see full table above).

• Results presentation:

  • Provide single-number quantity with margin.
  • Include maximum unfavourable deviation if > 8 dB.
  • Plot measurement and shifted reference curve as per ISO 140/3 and ISO 140/4.

Summary Diagram of Procedure

IS 11050 Part 1: Key Formulas, Tables & Specifications for Single-number Quantities

1. Reference Values (Table 3) for Airborne Sound Insulation (dB)

2. Single-number Quantities & Symbols

*Note: R' includes flanking transmission; primed symbols denote this.

3. Method of Comparison (Clause 4.3)

• Shift the reference curve in 1 dB steps towards measured data.
• Calculate mean unfavourable deviation (only where measured < reference).
• Shift to maximize mean deviation ≤ 2.0 dB.
• The shifted reference value at 500 Hz is the single-number quantity (e.g., Rw).
• Record max unfavourable deviation if > 8 dB.

IS 11050 Part 1: Reference Curves and Margins for Airborne Sound Insulation

Key Definitions:

• Margin (Ma or M'a): Shift of the reference curve to meet deviation limits (in dB).
  • Positive margin: curve shifted favorably
  • Negative margin: curve shifted unfavorably
• Relation:
  [ M_a = R_w - 52 \text{ dB}, \quad M'_a = R'_w - 52 \text{ dB} ]

Reference Values (Table 3):

Procedure to Evaluate Single-Number Quantities (Clause 4.3):

1. Shift reference curve in 1 dB steps towards measured values.
2. Calculate mean unfavourable deviation (only frequencies where measured < reference).
3. Stop when mean unfavourable deviation ≤ 2.0 dB and as large as possible.
4. Record the maximum unfavourable deviation if > 8 dB.
5. The shifted reference value at 500 Hz gives Rw, R'w, Dw, or DnT,w.

Summary of Single-Number Quantities (Table 1 & 2):

IS 11050 Part 1 - Key Formulas & Tables for Application to Building Elements

1. Method of Comparison (Clause 4.3)

• Shift the reference curve in 1 dB steps toward the measured curve.
• Calculate mean unfavorable deviation (only when measured < reference).
• Stop when mean deviation ≤ 2.0 dB and is maximized.
• The value at 500 Hz of shifted curve = Rw, R', Dw, or Dni,w.
• Record max unfavorable deviation if > 8 dB.

2. Single-Number Quantities (Tables 1 & 2)

3. Reference Values for Airborne Sound (Table 3)

4. Summary Diagram of Procedure

flowchart LR
   

IS 11050 Part 1 cross-references ISO 140 Parts 3 and 4 for airborne sound insulation measurement and evaluation.

Key Specifications & Tables

1. Method of Comparison (Clause 4.3)

• Shift the reference curve in 1 dB steps towards the measured one-third octave band values (100 Hz to 3150 Hz).
• Calculate mean unfavourable deviation (only where measurement < reference).
• Stop shifting when mean deviation ≤ 2.0 dB and as large as possible.
• Record maximum unfavourable deviation if > 8.0 dB.
• The shifted reference curve value at 500 Hz gives Rw, R'w, Dw, or DnT,w.

2. Reference Values (Table 3)

3. Single-Number Quantities (Tables 1 & 2)

IS 11050 Part 1: Notes and Explanatory Information Summary

Key Concepts:

• Method of Comparison (Clause 4.3):

  • Shift the reference curve (Table 3 values) in 1 dB steps towards measured values.
  • Calculate mean unfavourable deviation (only where measured < reference).
  • Maximize mean deviation ≤ 2.0 dB.
  • The shifted reference value at 500 Hz = Rw, Rw', Dw, or DnT,w.
  • Record max unfavourable deviation if > 8.0 dB.

• Statement of Results (Clause 5):

  • Report single-number quantities (Rw, R', Dw, DnT,w) with margins.
  • Include max unfavourable deviation if > 8.0 dB.
  • Provide measurement diagrams per ISO 140/3 & ISO 140/4.

Important Tables:

| Table 1: Single-number Quantities (Interior Elements) | |--------------------|---------|-----------------------------|---------|---------|--------| | Weighted sound reduction index | Rw | Sound reduction index (K) | ISO 140 Part 3 | Formula (3) | | Weighted apparent sound reduction index | R' | Apparent sound reduction index (R') | ISO 140 Part 4 | Formula (5)(6) |

| Table 2: Single-number Quantities (Between Rooms) | |--------------------|---------|-----------------------------|---------|---------|--------| | Weighted-level difference | Dw | Level difference (D) | ISO 140 Part 4 | Formula (2) | | Weighted standardized level difference | DnT,w | Standardized level difference (DAT) | ISO 140 Part 4 | Formula (3) |

| Table 3: Reference Values for Airborne Sound (dB) |