An audible emergency evacuation signal

IS 13735: Scope Overview

• Scope: IS 13735 specifies requirements for sound level meters used in environmental and industrial noise measurement, aligning with ISO 8201:1987.
• Application: Covers instruments for measuring sound pressure levels, frequency weightings, and time weightings relevant to noise assessment.

Key Specifications (from IS 13735 / ISO 8201):

Cross Reference Table

Summary Diagram

flowchart LR
    A[Sound Level Meter] --> B[Frequency Weighting (A, C, Z)]
    A --> C[Time Weighting (Fast, Slow, Impulse)]
    A --> D[Frequency Range (20 Hz - 8 kHz)]
    A --> E[Dynamic Range (30 - 130 dB)]
    A --> F[Microphone Type (Free-field/Random Incidence)]

For detailed formulas and calibration procedures, refer to IS 9779:1981 and IEC 651 standards.

IS 13735: Field of Application

IS 13735 covers design, construction, and testing of steel tubular poles for electrical and telecommunication purposes.

Key Specifications:

• Material: Steel tubular poles, hot-dip galvanized.
• Application: Overhead lines, street lighting, and telecommunication supports.
• Pole Types: Conical or tapered tubular poles.
• Design Loads: Wind loads as per IS 875 (Part 3), self-weight, and additional loads (e.g., equipment).

Important References:

• IS 875 (Part 3): Wind loads for design.
• ISO 8201: Steel tubular poles standards.

Typical Design Formulae:

• Wind Pressure:
  [ p = 0.6 \times V^2 \quad \text{(kN/m}^2\text{)} ]
  where (V) = design wind speed (m/s).

• Moment due to Wind Load:
  [ M = p \times A \times h ]
  where (A) = projected area, (h) = height of pole.

Summary Table:

flowchart LR
    A[Steel Tubular Poles] --> B[Design Loads]
    B --> C[Wind Load (IS 875)]
    B --> D[Self Weight]
    B --> E[Equipment Load]
    A --> F[Applications]
    F --> G[Electrical Lines]
    F --> H[Telecommunication]
    F --> I[Street Lighting]

For detailed design, refer to IS 13735 clauses and IS 875 for load calculations.

IS 13735: Key References and Cross References

• International Equivalent:
  IEC Pub 651 (Sound level meters) corresponds technically to IS 9779:1981.

• Temporal Patterns for Audible Signals (Clause 4.2):
  Audible emergency signals may be supplemented by visual/tactile signals for impaired hearing or high noise (>110 dB).

• Examples of Temporal Patterns:

  • Example 1: Steady tone signals (horns, buzzers) with temporal pattern.
  • Example 2: Sweep frequency or saw-tooth tones with frequency modulation during pulse.
  • Example 3: Two-tone high-low or low-high signals with frequency changes within pulses.
  • Example 4: Single-stroke bell or chime with "on" phase as striker actuation.

• Standard Mark Usage:
  BIS ensures quality compliance under the Bureau of Indian Standards Act, 1986.

Summary Table: Cross Reference of Standards

Visual Concept of Temporal Pattern (Example 1)

gantt
    title Temporal Pattern on Steady Tone Signal
    dateFormat  s
    section Signal On-Off
    On Pulse       :active, 0, 3
    Off Pulse      : 3, 2
    On Pulse       : 5, 3
    Off Pulse      : 8, 2

For detailed signal timing and frequency modulation patterns, refer to Figures 2-5 in IS 13735.

IS 13735: Audible Emergency Evacuation Signal - Key Requirements

1. Sound Pressure Level (SPL)

• Minimum SPL during "on" phase: ≥ 65 dB(A) above background noise (averaged over 60 s).
• If background noise > 110 dB(A), visual and tactile backup signals are mandatory.
• For waking sleeping occupants: ≥ 75 dB(A) at bedhead with doors closed (may not awaken all).

2. Temporal Pattern of Signal (Figure 1)

3. Measurement

• Use A-weighted sound pressure level with Fast time-weighting (F) per IEC 651.
• Background noise averaged over continuous 60 seconds.

4. Additional Notes

• Spectral content not specified; choose based on site/national rules.
• Visual/tactile signals must follow the same temporal pattern.

sequenceDiagram
    participant Signal
    Signal->>Room: ON for 0.5s (±10%)
    Signal-->>Room: OFF for 0.5s (±10%)
    Signal-->>Room: OFF for 1.5s (±10%)
    Note right of Signal: Cycle repeats every 4s (±10%)

This ensures the signal is audible, recognizable, and effective for emergency evacuation.

IS 13735: General Overview

IS 13735 primarily deals with sound level meters and related acoustic measurements.

Key Points:

• Field of Application: Covers specifications and requirements for sound level meters used in environmental noise measurement.
• Cross Reference: Equivalent to IEC Pub 651, ensuring international compatibility.
• Specifications: Refer to IS 9779:1981 for detailed sound level meter specs.

Typical Parameters & Formulas:

Important Notes:

• Sound Level Meter Types: Integrating, averaging, and octave band analyzers.
• Calibration: Regular calibration per IS 9779 is mandatory.
• Measurement Conditions: Ambient temperature, humidity, and wind affect readings.

flowchart TD
    A[Sound Source] --> B[Microphone]
    B --> C[Sound Level Meter]
    C --> D[Frequency & Time Weighting]
    D --> E[Display/Recording]

For detailed tables and exact tolerances, refer to IS 9779:1981 and IEC Pub 651.

IS 13735: Temporal Pattern for Audible Emergency Evacuation Signal

Key Specifications (Clause 4.2)

• Signal Pattern: "Three-pulse" temporal pattern.
• Pulse timing:
  • On phase (a): 0.5 s ±10%
  • Off phase (b): 0.5 s ±10%
  • Three successive on phases followed by off phase (c): 1.5 s ±10%
• Cycle repeats for a minimum of 180 seconds or as needed for evacuation.

Alternative (Single-stroke bell/chime)

• On interval: 1 s ±10%
• Off interval after each third on stroke: 2 s ±10%

Visual/Tactile Signals

• Use the same temporal pattern to assist hearing-impaired or in noisy environments (>110 dB background noise).

Temporal Pattern Summary Table

Application Examples (Annex)

• Steady tone signals (horns, buzzers) modulated with above pattern.
• Electronic sounders with frequency sweeps or two-tone signals.
• Single-stroke bells actuated per pulse timing.

Diagram of Temporal Pattern (Simplified)

gantt
    title Temporal Pattern (One Cycle)
    dateFormat  s
    axisFormat  %S s
    section Signal
    On (a)  :a1, 0, 0.5
    Off (b) :b1, after a1, 0.5
    On (a)  :a2, after b1, 0.5
    Off (b) :b2, after a2, 0.5
    On (a)  :a3, after b2, 0.5
    Off (c) :c1,

IS 13735: Recognition of Audible Emergency Evacuation Signals (Clause 4.3)

• Key Requirement:
  The "three-pulse" audible emergency evacuation signal must be clearly distinguishable from other signals (e.g., alarm signals) in the same area to avoid confusion.

• Reference:
  This aligns with ISO 7731 which governs safety signal characteristics.

• Additional Specification:
  If alarm signals are used in zones/floors not being evacuated, these signals must be significantly different in character from the "three-pulse" evacuation signal.

Summary Table: Signal Differentiation

Temporal Pattern Examples (from Annex, IS 13735):

• Example 1: Steady tone with three pulses
• Example 2: Sweep frequency with three pulses
• Example 3: Two-tone high-low or low-high with three pulses
• Example 4: Single-stroke bell with three pulses

sequenceDiagram
    participant Signal as Audible Signal
    participant Occupant as Occupant

    Signal->>Occupant: Three-pulse evacuation signal (distinct)
    Note right of Occupant: Recognizes evacuation alert

    Signal->>Occupant: Different alarm signal (non-evacuation)
    Note right of Occupant: Recognizes non-evacuation alert

Note: Ensure signal design complies with IS 13735 and ISO 7731 for clarity and safety.

IS 13735 - Sound Pressure Level (Clause 4.4) references IEC Pub 651 and IS 9779:1981 for sound level meters.

Key Points on Sound Pressure Level (SPL):

• Sound Pressure Level (Lp) is measured in decibels (dB) and defined as:

  [ L_p = 20 \log_{10} \left(\frac{p}{p_0}\right) ]

  where:

  • ( p ) = measured sound pressure (Pa)
  • ( p_0 = 20 \times 10^{-6} , \text{Pa} ) (reference sound pressure in air)

• Sound Level Meter Standards:

  • IEC Publication 651 defines types of sound level meters (Type 1 precision, Type 2 general purpose).
  • IS 9779:1981 specifies technical requirements for sound level meters used in India.

Typical Specifications (from IS 9779 / IEC 651):

Usage:

• Use A-weighting for general noise measurement (approximates human ear response).
• Use C-weighting for peak measurements or low-frequency noise.

flowchart LR
    Sound_Pressure[p (Pa)] -->|Measure| SPL_Calc[Calculate Lp = 20 log10(p/p0)]
    SPL_Calc -->|Output| SPL_dB[dB]
    SPL_dB -->|Compare| Limits[Noise Limits]

Summary: Measure sound pressure (p) with a calibrated sound level meter (IS 9779 compliant), apply weighting (A or C), then calculate SPL in dB using the logarithmic formula above.

IS 13735 - Duration and Temporal Pattern of Audible Emergency Evacuation Signal

Key Specifications (Clause 4.2 Temporal Pattern):

• Signal Pattern: "Three-pulse" temporal pattern
• On phase (a): 0.5 s ± 10%
• Off phase (b): 0.5 s ± 10%
• Number of pulses: 3 successive "on" periods
• Off phase (c): 1.5 s ± 10% after the 3 pulses
• Total cycle duration: Sum of above phases repeated continuously
• Minimum total duration: ≥ 180 seconds (3 minutes) for evacuation

Alternative Signal (Single-stroke bell/chime):

• On interval: 1 s ± 10%
• Off interval: 2 s ± 10% after every third "on" stroke

Temporal Pattern Diagram (Simplified):

gantt
    dateFormat  SS
    axisFormat  %S s
    section Three-pulse pattern
    On (a)       :active, 0, 0.5
    Off (b)      : 0.5, 0.5
    On (a)       : 1, 0.5
    Off (b)      : 1.5, 0.5
    On (a)       : 2, 0.5
    Off (c)      : 2.5, 1.5

Summary:

• The audible evacuation signal must be clearly distinguishable with precise on/off timing.
• The signal repeats continuously for at least 3 minutes.
• The pattern ensures easy recognition and effective evacuation alert.

For detailed examples, see annex of IS 13735.

IS 13735 - Supplementary Instructions (Clause 4.6)

• Purpose: To display a key word or phrase (e.g., "FIRE!", "GET OUT") during the "off" phase of a signal.
• Time Limit: The entire supplementary instruction must fit within the specified time limit c.
• Display: The phrase should be clearly visible and legible within the cycle time.

Key Points:

Visual Representation (Figure 1 Concept):

gantt
    title Supplementary Instruction Timing
    dateFormat  HH:mm:ss
    section Signal Cycle
    On Phase          :active, 0, 10s
    Off Phase         : 10s, 10s
    Supplementary Msg : 10s, 5s

• The supplementary message appears within the off phase and must complete before the next on phase.

Note: IS 13735 refers to ISO standards for emergency evacuation signals; check the standard for exact timing values and display requirements.

IS 13735: Visual and/or Tactile Signals for Emergency Evacuation

• Purpose: Supplement audible signals for hearing-impaired or noisy environments (>110 dB background noise).

• Temporal Pattern: Visual/tactile signals follow the same temporal pattern as audible signals (Clause 4.2).

• Supplementary Instructions: Key words/phrases (e.g., "FIRE!", "GET OUT") can be displayed during the "off" phase within specified time limits (Clause 4.6).

Key Points from IS 13735 (Clause 4.2 & 5):

Examples of Temporal Patterns (Annex - Non-mandatory):

Visual Summary (Mermaid.js):

flowchart TD
    A[Audible Signal] --> B[Temporal Pattern]
    B --> C[Visual Signal (Flashing Light)]
    B --> D[Tactile Signal (Vibration)] 
    style D fill:#f9f,stroke:#333,stroke-width:2px,color:#333
    note right of D: Not common in India
    B --> E[Supplementary Instructions]
    E --> F[Key Words/Phrases during "off" phase]

Note: For detailed timing and frequency parameters, refer to Clause 4.2

IS 13735: Temporal Pattern for Audible Emergency Signals

Key Specifications (Clause 4.2)

• Temporal pattern: "Three-pulse" pattern with:
  • On phase (a): 0.5 s ± 10%
  • Off phase (b): 0.5 s ± 10%
  • Repeat "on" and "off" phases 3 times consecutively
  • Off phase (c): 1.5 s ± 10% after the three pulses
• Minimum duration: Signal repeated for at least 180 seconds
• Example for single-stroke bell/chime:
  • On interval: 1 s ± 10%
  • Off interval after 3rd stroke: 2 s ± 10%

Application Notes

• Temporal pattern can be applied to various sound devices, including bells, chimes, electronic signals.
• Standardized pattern aids hearing-impaired by synchronizing with visual/tactile signals.
• Existing building devices can be adapted by imposing this pattern.
• New installations should select sound devices capable of penetrating background noise and apply this pattern.

Temporal Pattern Diagram (Figure 1 style):

gantt
    title Audible Signal Temporal Pattern
    dateFormat  SS
    axisFormat  %S

    section Signal
    On (a)     :active, 0, 0.5
    Off (b)    : 0.5, 0.5
    On (a)     : 1, 0.5
    Off (b)    : 1.5, 0.5
    On (a)     : 2, 0.5
    Off (c)    : 2.5, 1.5

This pattern repeats continuously for the evacuation duration.

For detailed frequency shifts or alternative patterns, refer to annex figures (3a, 3b, 4a, 4b) in IS 13735.