Rating of sound insulation in buildings and building elements, Part 3: Airborne sound insulation of facade elements and facades

IS 11050 Part 3: Scope and Field of Application

• Scope:
  Specifies methods to determine airborne sound insulation of building elements using measurements in one-third octave bands per ISO 140/3 and ISO 140/5.

• Field of Application:
  Applies to exterior building elements and façades for assessing airborne sound insulation.

Key Reference Values (Clause 4.2 & Tables)

• Reference values for comparison with measurements are given in Table 3 (not fully provided here).
• These values are frequency-dependent and used to calculate single-number ratings.

Important Tables (Summary)

Typical Formula for Single-Number Rating (e.g., Weighted Sound Reduction Index, Rw):

[ R_w = -10 \log_{10} \left( \frac{\sum_{i} 10^{-0.1 R_i} \cdot w_i}{\sum_i w_i} \right) ]

• (R_i) = sound reduction index in the i-th frequency band
• (w_i) = weighting factor from reference curve

flowchart LR
    A[Measurement in 1/3 Octave Bands] --> B[Obtain R_i values]
    B --> C[Compare with Reference Values (Table 3)]
    C --> D[Calculate Single-Number Rating (e.g., Rw)]
    D --> E[Assess Airborne Sound Insulation]

Summary: IS 11050 Part 3 guides measurement and evaluation of airborne sound insulation for building facades using standardized frequency bands and reference curves, enabling consistent single-number ratings for compliance and design.

IS 11050 Part 3: Normative References & Key Specifications

1. Reference Values (Clause 4.2 & Table 3)

Used for comparison with measured airborne sound insulation values (R, Rtr, Rg, etc.) at one-third octave bands:

2. Method of Comparison (Clause 4.3)

• Shift the reference curve in 1 dB steps towards measurement results.
• Calculate mean unfavourable deviation = sum of deviations where measured < reference / 16 frequencies.
• Maximize mean deviation ≤ 2.0 dB.
• Record Rw (or related indices) as the shifted reference value at 500 Hz.
• Report maximum unfavourable deviation if > 8 dB.

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

Summary Diagram of Procedure

flowchart TD
    A[Measure sound insulation values R, Rtr, etc.] --> B[Compare with reference values (Table 3)]
    B --> C[Shift reference curve

IS 11050 Part 3 – Key Terms, Definitions, and Specifications for Airborne Sound Insulation

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

2. Reference Values for Airborne Sound (Table 3)

3. Method of Comparison (Clause 4.3)

• Shift the reference curve in 1 dB steps toward the measured curve.
• Calculate mean unfavorable deviation (only where measured < reference).
• Stop when mean unfavorable deviation ≤ 2.0 dB and is maximum.
• The value at 500 Hz after shifting =

IS 11050 Part 3: Procedure for Evaluating Single-Number Quantities

This part aligns with ISO 717 and ISO 140 series for airborne sound insulation rating.

Key Points:

• Single-number quantities simplify acoustic requirements, derived from one-third octave band measurements.
• Terms and symbols differ by measurement type:
  • Table 1: Airborne sound insulation of exterior building elements.
  • Table 2: Airborne sound protection by façades.

Procedure Overview:

1. Measure sound insulation in one-third octave bands (ISO 140/3 & ISO 140/5).
2. Apply frequency weighting curves to the measured values.
3. Calculate single-number rating by comparing weighted values to reference curves.

Typical Formula (for airborne sound insulation index, e.g., Rw):

[ R_w = -10 \log_{10} \left( \sum_{i} 10^{-\frac{R_i}{10}} \times \Delta f_i \right) ]

• (R_i): Sound reduction index at frequency band (i)
• (\Delta f_i): Bandwidth weighting factor (usually constant for one-third octave bands)

Tables Summary (from IS 11050 Part 3):

flowchart TD
    A[Measure sound insulation in 1/3 octave bands] --> B[Apply frequency weighting curves]
    B --> C[Calculate single-number quantity]
    C --> D[Use in building code requirements]

Use IS 11050 Part 3 with ISO 140/3 & ISO 140/5 for detailed measurement and calculation procedures.

IS 11050 Part 3: Statement of Results - Key Formulas & Tables

1. Method of Comparison (Clause 4.3)

• Shift the reference curve in 1 dB steps towards the measured curve.
• Calculate mean unfavourable deviation = (Sum of unfavourable deviations) / 16 frequencies.
• Unfavourable deviation: when measured < reference at a frequency.
• Shift until mean unfavourable deviation ≤ 2.0 dB and as large as possible.
• Rw (or Rtr,w, Ro,w, etc.) = value of shifted reference curve at 500 Hz.
• Record maximum unfavourable deviation if > 8.0 dB.

2. Statement of Results (Clause 5)

• Report the single-number quantity (e.g., Rw, Rtr,w, DnT,tr,w).
• Report maximum unfavourable deviation if > 8.0 dB.
• Provide measurement results with a diagram, including the shifted reference curve (per ISO 140/3 & ISO 140/5).

3. Reference Values for Airborne Sound (Table 3)

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

IS 11050 Part 3: Reference Values for Airborne Sound Insulation

Key Concepts:

• Single-number quantities: Weighted indices derived from one-third octave band measurements.
• Measurement method: Shift a reference curve in 1 dB steps to minimize unfavorable deviations (where measured values < reference).
• Maximum unfavorable deviation: Should not exceed 2 dB on average; record if any frequency exceeds 8 dB.

Important Tables:

Table 1: Single-number quantities for exterior building elements

Table 2: Single-number quantity for façade airborne sound protection

Table 3: Reference values of airborne sound insulation (dB)

IS 11050 Part 3: Method of Comparison for Airborne Sound Insulation

Key Points from Clause 4.3: Method of Comparison

• Reference curve (Table 3 values) is shifted in 1 dB steps towards the measured curve.
• Calculate mean unfavourable deviation = sum of unfavourable deviations / 16 frequencies.
• Unfavourable deviation: when measured value < reference value at a frequency.
• Shift until mean unfavourable deviation is maximized but ≤ 2.0 dB.
• Record Rw (or Rtr,w, etc.) as the reference curve value at 500 Hz after shifting.
• If any unfavourable deviation > 8.0 dB, record the maximum deviation.

Table 3: Reference Values (dB) for Frequencies (Hz)

Formula Summary

[ \text{Mean unfavourable deviation} = \frac{\sum (\text{Reference value} - \text{Measured value})_{\text{if positive}}}{16} \leq 2.0 \text{ dB} ]

• Shift reference curve in 1 dB steps to maximize this mean deviation without exceeding 2.0 dB.
• The shifted reference curve value at 500 Hz = Rw (or respective symbol).

Result Reporting (Clause 5)

• Provide single-number quantity (Rw, Rtr,w, etc.).
• Report maximum unfavourable deviation if > 8 dB.
• Include diagram with shifted reference curve per ISO 140/3 and ISO

IS 11050 Part 3: Airborne Sound Insulation of Facade Elements and Facades

This part focuses on airborne sound insulation for facades, including windows, doors, and roofs.

Key Concepts & Formulas

• Sound Reduction Index (R):
  Measures the ability of a facade element to reduce sound transmission.
  [ R = 10 \log_{10} \left(\frac{1}{T}\right) ]
  where (T) = sound transmission coefficient.

• Weighted Sound Reduction Index (R_w):
  A single-number rating derived from frequency-dependent R values, standardized to compare elements.

• Facade Sound Insulation Index (D2m,nT,w):
  Accounts for facade sound insulation considering outdoor sound pressure levels and reverberation time indoors.

Typical Tables (from IS 11050 & related standards)

Application Guidelines

• Use double/triple glazing for better sound insulation.
• Seal gaps around facade elements to avoid sound leaks.
• Combine facade elements with absorptive materials inside rooms to improve overall sound insulation.

flowchart LR
  A[Outdoor Noise] --> B[Facade Element]
  B --> C[Sound Transmission]
  C --> D[Indoor Noise Level]
  B --> E[Sound Reduction Index (R)]
  E --> F[Weighted Index (R_w)]
  F --> G[Facade Sound Insulation (D2m,nT,w)]

For detailed field measurement procedures, refer to IS 11050 Part 5.

Weighted Sound Reduction Indices (IS 11050 Part 3 / ISO 717-3)

Key Concepts:

• Weighted sound reduction indices (e.g., Rw, Rtr,w, Row, Re,oc,w) are single-number quantities derived from one-third octave band measurements.
• The indices evaluate airborne sound insulation of building elements and façades.

Method of Comparison (Clause 4.3):

• Shift the reference curve in 1 dB steps towards the measured curve.
• Calculate the mean unfavourable deviation (only where measured < reference).
• Shift stops when mean deviation ≤ 2 dB and is maximized.
• The reference curve value at 500 Hz after shifting is the weighted index (e.g., Rw).
• Record max unfavourable deviation if > 8 dB.

Reference Values for Airborne Sound (Table 3):

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

Weighted Standardized Level Difference (DnT,tr,w) as per IS 11050 Part 3 (ISO 717-3):

Key Concept:

• It is a single-number quantity representing airborne sound protection by façades.
• Derived from one-third octave band values of standardized level difference (DnT,tr).
• Calculated by shifting a reference curve to fit measurement data.

Procedure (Clause 4.3):

1. Measure DnT,tr in 1/3 octave bands (preferably to one decimal place).
2. Shift the reference curve (Table 3 values) in 1 dB steps towards the measured curve.
3. Calculate the mean unfavourable deviation (only where measured < reference).
4. Stop when mean unfavourable deviation ≤ 2 dB and as large as possible.
5. The value at 500 Hz on the shifted reference curve is the weighted level difference DnT,tr,w.
6. Record max unfavourable deviation if > 8 dB.

Reference Values (Table 3 excerpt):

Summary formula:

• DnT,tr,w = Reference curve value at 500 Hz after shifting
• Shift reference curve to minimize unfavourable deviations ≤ 2 dB.

Illustration of the shifting process:

graph LR
A[Measured DnT,tr values] --> B[Compare with Reference Curve]
B --> C{Shift reference curve in 1 dB steps}
C --> D[Calculate mean unfavourable deviation]
D --> E{Deviation ≤ 2 dB

IS 11050 Part 3 – Reporting & Documentation Requirements:

Key Points:

• Single-number quantities (e.g., Rw, Rtr,w, DnT,tr,w) are derived from one-third octave band measurements as per ISO 140/3 & ISO 140/5.
• Reference values for airborne sound at specific frequencies are given in Table 3 (in dB):

Method of Comparison (Clause 4.3):

• Shift the reference curve in 1 dB steps toward measured data.
• Calculate mean unfavourable deviation (only where measurement < reference).
• Shift until mean deviation ≤ 2 dB and maximum unfavourable deviation ≤ 8 dB.
• The value at 500 Hz on shifted curve = Rw (or relevant index).
• Report maximum unfavourable deviation if > 8 dB.

Documentation (Clause 5):

• Report the single-number quantity with reference to ISO 717.
• Include maximum unfavourable deviation if > 8 dB.
• Provide measurement results as a diagram showing:
  • Measured values,
  • Shifted reference curve (per ISO 140/3 & ISO 140/5).

Summary Diagram of Reporting Process:

flowchart TD
    A[Measure sound insulation in 1/3 octave bands] --> B[Compare with reference values (Table 3)]
    B --> C[Shift reference curve in 1 dB steps]
    C --> D[Calculate mean unfavourable deviation]
   

IS 11050 Part 3 references ISO 717-3 (1982) for airborne sound insulation measurement and evaluation.

Key Specifications and Tables

1. Reference Values for Airborne Sound (Table 3)

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

3. Method of Comparison (Clause 4.3)

• Shift the reference curve in 1 dB steps towards measured values.
• Calculate mean unfavorable deviation (only where measured < reference).
• Maximize mean deviation ≤ 2 dB.
• Rw (or respective index) = reference value at 500 Hz after