hearing.occupational_exposure

Occupational noise exposure: measurement strategies and uncertainty (ISO 9612:2009).

ISO 9612:2009 is the engineering method (accuracy grade 2) for determining a worker’s daily noise exposure level LEX,8h from measurements of the A-weighted equivalent continuous sound pressure level Lp,A,eqT. The raw levels themselves come from the dosimetry primitives in phonometry.levels (leq/lex_8h); this module adds the three measurement strategies, the energy combination of their contributions, and the normative Annex C uncertainty budget.

Three strategies (Clause 8):

• Task-based (Clause 9): the nominal day is split into tasks; each task level is the energy average of I >= 3 samples (Eq 7), its contribution is LEX,8h,m = Lp,A,eqT,m + 10 lg(T_m/T0) (Eq 8), and the daily level is the energy sum over tasks (Eq 9/10).
• Job-based (Clause 10): N >= 5 random samples over a homogeneous exposure group; the effective-day level is their energy average (Eq 11) and LEX,8h = Lp,A,eqTe + 10 lg(Te/T0) (Eq 12). The minimum cumulative measurement duration follows Table 1.
• Full-day (Clause 11): three (or more) whole-day measurements averaged (Eq 11), then Eq 13, the same arithmetic as the job method.

Uncertainty (Annex C, normative). Combined u^2 = sum c_i^2 u_i^2 (C.1), expanded U = k*u with k = 1.65 for a one-sided 95 % confidence interval (Clause 14). Task-based uses Eq C.3 with sampling u1a (C.6), duration u1b (C.7) and sensitivity coefficients c1a (C.4)/c1b (C.5). Job-based and full-day use Eq C.9 with c1*u1 read from Table C.4 and c2 = c3 = 1. The instrument standard uncertainty u2 is from Table C.5 and the microphone position u3 = 1.0 dB (C.6). Peak levels Lp,Cpeak are reported without an uncertainty: Annex C gives no method for them (Table C.5, NOTE 1).

The three worked examples of Annexes D (task), E (job) and F (full-day) are reproduced to the standard’s printed precision in the test suite (Annex E rounds its effective-day level to 88.4 dB before Eq 12 and prints 88.1; the library keeps intermediates unrounded and yields 88.2). Clause/equation/table numbers refer to ISO 9612:2009(E).

Auto-generated from the source docstrings by scripts/generate_api_docs.py (make api-docs). Do not edit by hand.

COVERAGE_FACTOR

Constant (float).

COVERAGE_FACTOR = 1.65

ExposureResult

ExposureResult(
    lex_8h: float,
    combined_standard_uncertainty: float,
    expanded_uncertainty: float,
    strategy: str,
    coverage_factor: float = 1.65,
    lp_aeqte: float | None = None,
    effective_duration_hours: float | None = None,
    u1: float | None = None,
    c1u1: float | None = None,
    u2: float | None = None,
    u3: float | None = None,
    n_samples: int | None = None,
    sampling_advisory: bool = False,
    instrument: InstrumentClass | None = None,
    tasks: tuple[TaskContribution, ...] = ...,
)

Daily noise exposure level and its expanded uncertainty (ISO 9612:2009).

Attributes

Name	Description
lex_8h	A-weighted daily noise exposure level LEX,8h, dB.
combined_standard_uncertainty	Combined standard uncertainty u (Eq C.1), dB.
expanded_uncertainty	Expanded uncertainty U = 1.65*u for a one-sided 95 % confidence interval, dB.
strategy	"task", "job" or "full_day".
instrument	Instrument class the measurement was made with (the call default; individual tasks may override it): "class1", "class2" or "personal_exposimeter". Printed on the .report() fiche (ISO 9612:2009 Clause 15 c).
upper_limit	LEX,8h + U, the value 95 % of readings fall below.

ExposureResult.plot()

ExposureResult.plot(
    ax: Axes | None = None,
    *,
    language: str = 'en',
    **kwargs: Any,
) -> Axes

Plot the per-task contributions with the LEX,8h line.

Only task-based results carry per-task contributions (the job and full-day strategies raise ValueError). Requires matplotlib (pip install phonometry[plot]); returns the Axes.

ExposureResult.report()

ExposureResult.report(
    path: str,
    *,
    metadata: ReportMetadata | None = None,
    engine: str = 'reportlab',
    verbose: bool = False,
    language: str = 'en',
) -> str

Render an ISO 9612 occupational noise-exposure fiche to a PDF.

Writes a one-page measurement report with the information ISO 9612:2009 Clause 15 asks for: the standard-basis line naming the applied strategy, a metadata header (company, worker/job, workplace, instrumentation, calibration), the work analysis (the per-task table of durations, Lp,A,eqT,m levels and LEX,8h,m contributions for the task-based strategy, or the sampling summary for the job-based/full-day strategies), the per-task contribution chart for a task-based result, the boxed LEX,8h with its expanded uncertainty U stated separately (Clause 15 e), an assessment table against the exposure action values (80/85 dB(A)) and the exposure limit value (87 dB(A)) of Directive 2003/10/EC, a PASS/FAIL verdict against the limit value, and a footer identity/disclaimer block.

Parameters

Name	Description
path	Destination path of the PDF file.
metadata	Optional ReportMetadata supplying the header identity (client is the company, specimen the worker(s)/job, test_room the workplace) plus the instrumentation and calibration free-text fields and the footer identity.
engine	Rendering back end; only "reportlab" is supported.
verbose	When True, the task-based work-analysis table adds the Annex C per-task uncertainty columns (u1a, u1b, u2). The job-based/full-day sampling summary always shows its budget.
language	Fiche language: "en" (default, English) or "es" (Spanish, with a comma decimal separator).

Returns: The written path as a str.

Raises

Exception	When
ValueError	If engine is not "reportlab" or language is unknown.
ImportError	If reportlab (or, for a task-based result’s chart, matplotlib) is not installed (pip install phonometry[report]).

ExposureResult.upper_limit

property

Upper limit LEX,8h + U of the one-sided 95 % interval, dB.

full_day_exposure

full_day_exposure(
    samples: Sequence[float],
    effective_duration_hours: float,
    instrument: InstrumentClass = 'personal_exposimeter',
    u3: float = 1.0,
    warn: bool = True,
) -> ExposureResult

Daily noise exposure level from full-day measurements (ISO 9612:2009 Clause 11).

Three (or more) whole-day Lp,A,eqT measurements are energy-averaged (Eq 11) and the daily level follows Eq 13. If only three measurements are supplied and they span 3 dB or more, Clause 11.3 requires at least two more; this raises the sampling advisory. The uncertainty is the job-based budget (Eq C.9, Table C.4).

Parameters

Name	Description
samples	Whole-day Lp,A,eqT,n measurements, dB (three minimum per Clause 11.3; two is enforced numerically).
effective_duration_hours	Effective working-day duration T_e, hours.
instrument	Instrument class selecting u2 (Table C.5).
u3	Microphone-position standard uncertainty, dB (Clause C.6 gives 1.0).
warn	Emit OccupationalExposureWarning for the 3 dB spread rule and the Table C.4 advisory.

Returns: An ExposureResult.

INSTRUMENT_U2

Constant (dict).

INSTRUMENT_U2 = {'class1': 0.7, 'class2': 1.5, 'personal_exposimeter': 1.5}

job_based_exposure

job_based_exposure(
    samples: Sequence[float],
    effective_duration_hours: float,
    instrument: InstrumentClass = 'personal_exposimeter',
    u3: float = 1.0,
    n_workers: int | None = None,
    sample_duration_hours: float | None = None,
    warn: bool = True,
) -> ExposureResult

Daily noise exposure level from job-based measurements (ISO 9612:2009 Clause 10).

The effective-day level is the energy average of N >= 5 random job samples (Eq 11); the daily level follows Eq 12. The sampling uncertainty u1 is the sample standard deviation (Eq C.12) and its contribution c1*u1 is read from Table C.4; the combined uncertainty is Eq C.9 with c2 = c3 = 1.

Parameters

Name	Description
samples	Measured Lp,A,eqT,n job samples, dB (at least five per Clause 10.2; a minimum of two is enforced numerically).
effective_duration_hours	Effective working-day duration T_e, hours.
instrument	Instrument class selecting u2 (Table C.5).
u3	Microphone-position standard uncertainty, dB (Clause C.6 gives 1.0).
n_workers	Optional homogeneous-group size n_G; when given with sample_duration_hours, the cumulative duration is checked against Table 1 and an advisory is raised if it falls short.
sample_duration_hours	Optional per-sample duration (hours) for the Table 1 cumulative-duration check.
warn	Emit OccupationalExposureWarning for the Table C.4 / Table 1 advisories.

Returns: An ExposureResult.

minimum_cumulative_duration_hours

minimum_cumulative_duration_hours(n_workers: int) -> float

Minimum cumulative measurement duration (h) for a homogeneous exposure group (Table 1).

Parameters

Name	Description
n_workers	Number of workers n_G in the homogeneous exposure group.

Returns: The minimum cumulative measurement duration in hours. For n_G > 40 the standard advises splitting the group; the returned 17 h is the tabulated fallback.

OccupationalExposureWarning

Advisory raised when an ISO 9612 sampling rule recommends more measurements.

table_c4_contribution

table_c4_contribution(n_samples: int, u1: float) -> float

Uncertainty contribution c1*u1 (dB) from Table C.4 (job/full-day sampling).

Bilinear interpolation on the sample count N and the sampling standard uncertainty u1. The u1 axis is anchored at the origin (u1 = 0 gives 0 dB) and both axes are clamped to the tabulated range [3, 30] x [0, 6]. Rows N = 3 and N = 4 apply to full-day measurements only (ISO 9612:2009 Table C.4, NOTE 1).

Parameters

Name	Description
n_samples	Number of job/full-day samples N (>= 2).
u1	Standard uncertainty of the samples, dB (>= 0).

Returns: The contribution c1*u1 in dB.

Task

Task(
    samples: tuple[float, ...],
    duration_hours: float,
    duration_samples: tuple[float, ...] | None = None,
    duration_range: tuple[float, float] | None = None,
    label: str | None = None,
    instrument: InstrumentClass | None = None,
)

One task of a task-based measurement (ISO 9612:2009 Clause 9).

Parameters

Name	Description
samples	Measured Lp,A,eqT,mi levels for the task, dB. At least three are recommended (Clause 9.3); a single conservative value is allowed for negligible tasks (its u1a is then zero).
duration_hours	Arithmetic mean task duration T_m (Eq 5), hours.
duration_samples	Optional independent duration observations T_m,j (hours) used for u1b via Eq C.7.
duration_range	Optional (T_min, T_max) range (hours); u1b is then 0.5*(T_max - T_min) (Eq C.7 NOTE). Ignored if duration_samples is given.
label	Optional human-readable task name.
instrument	Optional per-task instrument class overriding the call default (selects u2 from Table C.5).

task_based_exposure

task_based_exposure(
    tasks: Sequence[Task],
    instrument: InstrumentClass = 'personal_exposimeter',
    u3: float = 1.0,
    include_duration_uncertainty: bool = True,
    warn: bool = True,
) -> ExposureResult

Daily noise exposure level from task-based measurements (ISO 9612:2009 Clause 9).

Each task level is the energy average of its samples (Eq 7); the daily level is the energy sum of the task contributions (Eq 9/10). The uncertainty budget follows Eq C.3 with sampling u1a (Eq C.6), optional duration u1b (Eq C.7), and sensitivity coefficients c1a (Eq C.4) and c1b (Eq C.5).

Parameters

Name	Description
tasks	The tasks making up the nominal day.
instrument	Default instrument class selecting u2 (Table C.5); may be overridden per Task.
u3	Microphone-position standard uncertainty, dB (Clause C.6 gives 1.0).
include_duration_uncertainty	Include the (c1b*u1b)^2 duration term (Eq C.3). When False the budget omits it (ISO 9612 Annex D case a).
warn	Emit OccupationalExposureWarning when a task triggers the 3 dB spread rule (Clause 9.3).

Returns: An ExposureResult with per-task contributions.

TaskContribution

TaskContribution(
    label: str,
    lp_aeqt: float,
    duration_hours: float,
    lex_8h_contribution: float,
    n_samples: int,
    sample_range_db: float,
    spread_advisory: bool,
    u1a: float,
    c1a: float,
    u1b: float,
    c1b: float,
    u2: float,
    u3: float,
)

Per-task results and uncertainty terms of a task-based determination.

TaskContribution.variance_contribution

property

This task’s contribution to u^2(LEX,8h) (a term of Eq C.3), dB².