Rating of sound insulation in buildings and of building elements, Part 2: Impact sound insulation
1984 Edition

Scope and Application in Impact Sound Insulation Evaluation

• Scope:
  Defines the approach to derive acoustic parameters from measurements conducted in one-third octave bands following ISO 140/6 and ISO 140/7 methodologies. It targets the assessment of sound insulation characteristics in building structures.

• Application Area:
  Mainly used to benchmark measured acoustic results against established reference values for performance verification.

• Reference Values (Clause 4.2):
  Presented in Table 3 of the standard, these serve as the baseline for comparative analysis.

Highlights:

• Utilizes one-third octave band measurement data.
• Employs Table 3 reference values for assessment.
• Applicable primarily to building acoustical evaluations, especially concerning impact sound insulation.

Sample Reference Values Table (Indicative):

(Refer to IS 11050 Part 2 Table 3 for precise figures)

flowchart TD
    A[Collect 1/3 Octave Band Data] --> B[Apply ISO 140/6 & ISO 140/7 Procedures]
    B --> C[Calculate Acoustic Quantities]
    C --> D[Contrast with Reference Values (Table 3)]
    D --> E[Evaluate Acoustic Performance]

For exact parameters and formulas, consult the official IS 11050 Part 2 Table 3 and corresponding ISO standards.

Normative References and Baseline Values in IS 11050 Part 2

1. Normative References

• This standard relies on international and Indian standards for definitions, measurement techniques, and procedural consistency.
• Referenced documents ensure uniformity and comparability in acoustic evaluations.

2. Clause 4.2: Reference Values (Table 3)

• Table 3 lists the benchmark values against which measurement outcomes are compared.
• These values are crucial for verifying compliance with acoustic performance limits.
• Typically, the table includes:
  • Frequency bands
  • Threshold values (e.g., velocity or acceleration limits in mm/s or m/s²)
  • Specific measurement scenarios

3. Essential Details

• Reference values act as standard thresholds.
• Deviations beyond these values imply non-conformance or the need for remedial measures.
• Graphical representations illustrate acceptable ranges across frequency bands.

Example Reference Values Table Structure:

flowchart LR
    A[Measurement Output] --> B{Compare to Reference Limits}
    B -->|Within Limits| C[Compliant]
    B -->|Exceeds Limits| D[Non-compliant - Action Required]

Summary: Always refer to Table 3 in IS 11050 Part 2 for the definitive reference values to evaluate measurement data.

Key Terms and Definitions in IS 11050 Part 2

• Terminology may differ slightly from other Indian Standards; cross-referencing should be done carefully.
• Reference Values (Clause 4.2):
  Employed for comparative evaluation of noise and vibration measurements.
• Measurements are processed in one-third octave bands as per ISO 140/6 and ISO 140/7.
• The standard details calculations for deriving acoustic quantities (e.g., sound levels and indices) from banded frequency data.

Conceptual Overview of Reference Values:

Sample Calculation from ISO 140 Series:

[ L_{total} = 10 \log_{10} \left( \sum_{i} 10^{L_i/10} \right) ]

• (L_i): Level measured in the ith one-third octave band.

flowchart LR
    A[Obtain 1/3 Octave Band Data] --> B[Apply Reference Values (Table 3)]
    B --> C[Compute Weighted Acoustic Levels]
    C --> D[Derive Noise and Vibration Indices]

For precise definitions and tables, consult IS 11050 Part 2 and ISO 140/6 & 140/7.

Guidelines for Calculating Single-Number Impact Sound Insulation Quantities (Ln,w) in IS 11050 Part 2

This procedure corresponds with ISO 717 and ISO 140 standards for impact sound rating.

Fundamental Concepts:

• Single-number quantity (Ln,w): Represents a weighted and normalized impact sound pressure level.
• Margin (Mi): Vertical shift applied to the reference curve to align with measured data, defined as: [ M_i = 60,dB - L_{n,w} ] where ( L_{n,w} ) is the resulting single-number rating.

Stepwise Summary:

1. Perform impact sound level measurements in one-third octave bands as per ISO 140/6 and 140/7.
2. Plot the measured spectrum against the standard reference curve.
3. Vertically shift the reference curve by margin Mi to minimize deviations within permissible limits.
4. Calculate (L_{n,w}) from the shifted curve using: [ L_{n,w} = 60,dB - M_i ]

Notes:

• A positive margin (Mi) indicates improved insulation relative to the reference.
• This approach simplifies complex spectral data into a single rating for regulatory use.

Table: Correlation Between Margin and Single-Number Rating

flowchart TD
    A[Measure impact sound (ISO 140/6 & 140/7)] --> B[Plot spectrum in 1/3 octave bands]
    B --> C[Shift reference curve by margin Mi]
    C --> D[Compute Ln,w = 60 - Mi]
    D --> E[Apply Ln,w for building regulation compliance]

This streamlined procedure guarantees consistent and reproducible impact sound insulation ratings.

Guidance on Presenting Results in IS 11050 Part 2

1. Reference Values Usage (Clause 4.2)

• Reference values from Table 3 are essential for benchmarking measurement results.
• Measurements are conducted in one-third octave bands according to ISO 140/6 and ISO 140/7.

2. Deriving Acoustic Quantities

• Data is integrated and weighted across frequency bands.
• Standard frequency weightings (such as A-weighting) are applied in line with ISO protocols.

3. Single-Number Ratings

• Octave band data is condensed into single-number indices (e.g., DnT, Rw) using prescribed methods.
• The typical computation for Rw is:

[ Rw = 10 \log_{10} \left( \sum_{i} 10^{L_i/10} \right) ]

where (L_i) represents corrected sound levels per band.

4. Example Reference Values Table

(Exact figures should be obtained from IS 11050 Table 3)

flowchart LR
    A[Collect 1/3 Octave Band Data] --> B[Apply Necessary Corrections]
    B --> C[Compare Against Reference Values (Table 3)]
    C --> D[Compute Single-Number Ratings]
    D --> E[Compile Statement of Results]

Summary: Employ reference values from Table 3, perform measurements in one-third octave bands per ISO 140 standards, apply corrections, and calculate single-number ratings for final reporting.

Recommended Method for Evaluating Weighted Impact Sound Improvement Index (ΔLw) of Floor Coverings as per IS 11050 Part 2

Overview:

• The weighted impact sound improvement index (ΔLw) quantifies the reduction in impact noise due to floor coverings.
• Measurements are carried out either in laboratory conditions (IS 11050 Part 8) or in situ (Part 7) using a standardized tapping machine (Part 6).

Procedure:

1. Measure the weighted normalized impact sound pressure level (L_n,w) of the bare floor.
2. Measure L_n,w with the floor covering installed under identical conditions.
3. Calculate the improvement index: [ \Delta L_w = L_{n,w, \text{bare}} - L_{n,w, \text{covered}} ]

Details:

• Measurements span frequencies from approximately 100 Hz to 3150 Hz.
• Frequency weighting is applied to obtain a single-number ΔLw.

Illustrative Values:

flowchart LR
    A[Measure L_n,w of bare floor] --> B[Install floor covering]
    B --> C[Measure L_n,w of covered floor]
    C --> D[Calculate ΔLw = L_n,w,bare - L_n,w,covered]
    D --> E[Assess impact sound reduction effectiveness]

This method aligns with IS 11050 Parts 6 through 8 and international standards for evaluating impact sound insulation of floor coverings.

Recommended Approach for Determining Equivalent Weighted Normalized Impact Sound Pressure Level (Ln,w,eq) for Bare Concrete Floors as per IS 11050 Part 2 / ISO 717-2

1. Key Terms

• Ln,w: Weighted normalized impact sound pressure level for the bare floor.
• ΔLw: Weighted impact sound improvement index provided by floor coverings.
• Ln,w,eq,o: Equivalent weighted normalized impact sound pressure level of the bare concrete floor considering a reference floor covering.

2. Reference Curve Adjustment (Clause 4.3)

• Shift the standard reference curve (from Table 3) in 1 dB increments to minimize mean unfavorable deviation to ≤ 2 dB.
• Only deviations where the measured values exceed the reference curve are considered.
• Ln,w is defined at the 500 Hz point on the adjusted reference curve.
• Record the maximum unfavorable deviation if it exceeds 8 dB.

3. Reference Values for Impact Sound (Excerpt from Table 3)

4. Reference Floor Characteristics (Annex A.3, Table 4)

• The weighted normalized impact sound pressure level of the reference floor, Ln,w,r,o, is 78 dB.

5. Calculation (Annex A.4)

[ \begin{align*} Ln,r &= Ln,r,0 - AL \ AL_w &= Ln,w,r,o - Ln,w,r = 78,dB - Ln,w,r \end{align*} ]

where:

• AL: Reduction in impact sound pressure due to floor covering.
• Ln,r: Normalized impact sound pressure level of the reference floor with covering.
• Ln,w,r: Weighted normalized impact sound pressure level after reference curve shift.

6. Equivalent Weighted Normalized Impact Sound Level

The equivalent level Ln,w,eq is derived considering the reference floor covering and measured data, facilitating standardized comparison across bare concrete floors.