Overview
IEC 61606-4:2005 - part of the IEC 61606 series - defines basic measurement methods for digital audio parts of personal computers (PCs). It specifies how to measure a linear PCM (LPCM) signal for both desktop and portable computers, covering digital‑in/analogue‑out and analogue‑in/digital‑out paths. The standard references common measurement conditions from IEC 61606-1 and provides PC‑specific conditions, test media and setup conventions. Targeted sampling frequencies span 8 kHz to 192 kHz and bit depths 8 to 24 bits; it excludes bit‑rate reduced formats and 1‑bit signals.
Key Topics and Technical Requirements
- Scope and applicability: Measurement methods for LPCM audio in PC audio subsystems (internal HDD or main memory as test media). Excludes purely analogue/analogue and digital/digital measurements covered elsewhere.
- Measuring conditions: Environmental and power supply tolerances, standard and working settings, preconditioning requirements and factory defaults.
- Signal levels and impedances: Defined standard input/output amplitudes (e.g., 2 V r.m.s. analogue terminals; 100 mV r.m.s. microphone), normal measuring amplitude (1/10 of standard), source/load impedances (analogue input 2.2 kΩ, mic 600 Ω; output loads 22 kΩ, headphone 32 Ω, speaker 8 Ω).
- Test media and storage: Definitions for standard medium, working medium and recording medium - typically internal HDD or equivalent main memory.
- Measuring instruments: Requirements for analogue signal generators, in‑band level meters, analogue filters and weighting filters, recording/standard media and software for digital data evaluation.
- Measurement methods and metrics: Detailed procedures, block diagrams and test methods for:
- Input/output characteristics and gain tracking
- Frequency response
- Noise characteristics (S/N ratio, dynamic range)
- Distortion characteristics (THD, short‑term distortion)
- Channel separation and crosstalk
- Digital pathways: Specific treatment for analogue‑in/digital‑out and digital‑in/analogue‑out measurement chains, including recording and playback considerations.
Applications and Users
- Who uses it: Test engineers, audio hardware designers, PC OEMs, compliance laboratories and QA teams measuring PC audio performance.
- Practical uses:
- Validating audio I/O performance of notebooks, desktops and embedded PC systems
- Comparing codec/ADC/DAC implementations and driver/software impacts
- Creating product datasheets with standardized S/N, THD, frequency response and dynamic range figures
- Ensuring reproducible lab measurements for R&D and acceptance tests
Related Standards
Keywords: IEC 61606-4, digital audio measurement, personal computer audio, PCM measurement methods, frequency response, signal-to-noise ratio, distortion, dynamic range, PC audio testing.