Ear Entrance Point

Description

The Ear Entrance Point (EEP) is a standardized anatomical reference point used in 3GPP audio performance testing specifications. It is defined as the point in space located at the entrance to the ear canal. This point serves as the critical reference for positioning artificial test equipment, such as Head and Torso Simulators (HATS) with ear simulators, during objective measurements of audio transmission quality, loudness, and frequency response for terminals like mobile phones, headsets, and hands-free systems.

In testing architecture, the EEP is not a physical component but a conceptual landmark. The primary physical apparatus is a standardized ear simulator (as defined in ITU-T P.57), which is a coupler designed to mimic the acoustic impedance and volume of an average human ear canal. This ear simulator is mounted within an artificial head or torso. The EEP is the point in space at the opening of this ear simulator's canal. During testing, the device under test (DUT), such as a handset's earpiece or a headset's speaker, is carefully positioned relative to this EEP according to strict geometric alignment defined in test standards (e.g., the 'cheek' or 'touch' position).

The role of the EEP is to ensure reproducibility. Audio characteristics like sound pressure level (loudness), frequency response, and sidetone are highly sensitive to the precise distance and angle between the sound source and the ear. By defining a fixed, unambiguous reference point, 3GPP ensures that different manufacturers and test laboratories around the world align their DUTs in the same way. This allows for fair, comparable, and repeatable measurements of key performance indicators (KPIs) such as Send Loudness Rating (SLR), Receive Loudness Rating (RLR), and Total Harmonic Distortion (THD).

Measurements proceed by generating or capturing test signals through the DUT while it is acoustically coupled to the ear simulator at the EEP. The signal is analyzed by measurement equipment connected to the ear simulator's microphone. The entire chain—from the DUT's audio codec and speaker, through the air gap to the EEP, into the ear simulator, and to the analyzer—is calibrated against this reference point. This standardization is fundamental for validating that devices meet minimum audio quality requirements for network interoperability and user experience.

Purpose & Motivation

The EEP was standardized to solve the problem of inconsistent and non-reproducible audio testing for telecommunications terminals. Before such precise definitions, different test labs might position devices slightly differently relative to dummy heads or ears, leading to significant variation in measured loudness and frequency response. This made it difficult to objectively compare devices, enforce quality standards, and guarantee a consistent user experience across the industry.

The historical motivation stems from the need for network operators and standards bodies to define clear, pass/fail criteria for type approval of handsets. As digital speech codecs (like AMR, EVS) evolved, accurately measuring their performance in a realistic acoustic environment became critical. The EEP, along with the entire Head and Torso Simulator framework, provides the controlled, anthropomorphic 'acoustic interface' needed to translate electrical signals from the codec into perceived acoustic performance.

This reference point addresses the limitations of simpler electrical loopback testing. Audio quality is ultimately perceived by the human ear, which is influenced by the device's acoustics, the ear's geometry, and the positioning. By anchoring tests to the EEP, 3GPP creates a proxy for the real human listening experience in a lab environment. It ensures that devices meeting the standard will provide adequate and consistent loudness and fidelity to end-users, regardless of who manufactured the device or where it was tested.

Key Features

• Standardized anatomical reference point at the entrance to the ear canal
• Foundation for reproducible positioning of terminals during acoustic tests
• Used with artificial head and torso simulators (HATS) and ear simulators
• Critical for measuring Receive Loudness Rating (RLR) and Send Loudness Rating (SLR)
• Enables comparable frequency response and distortion measurements across labs
• Defined in conjunction with specific cheek and touch handset positions for testing

Evolution Across Releases

Defining Specifications