Description

When purchasing a refurbished or second-hand mobile phone, ensuring it meets your expectations is crucial - and audio quality is no exception. Whether you are a music enthusiast, rely on crystal-clear call quality, or use your phone for video streaming, a phone's audio performance can significantly impact your experience. This article explores how robot-assisted testing can be used to ensure the high audio quality of tested second-hand phones.

Defect Categories

Speakers

Typically, a mobile phone has two audio speakers: a receiver/earpiece speaker and the main loudspeaker. The former is used during calls, while the latter is used for tasks such as playing music or video audio.
Physical wear can lead to crackling, distortion, or reduced volume in second-hand mobile phone speakers. Dirt, dust, or moisture can also degrade speaker performance over time.

Microphones

When recording audio or making a call, the mobile phone uses different microphones depending on what is needed. Typically, there are three microphones: a bottom microphone, used for general audio input and for capturing the user's voice during calls. A top microphone, located near the top edge of the phone, is used for noise cancellation and background noise filtering purposes. Lastly, a microphone positioned near the camera module on the back of the phone is used for recording audio during video capture.
Over time, microphones can degrade due to dust, debris, or wear and tear, leading to muffled or distorted recordings and bad voice quality in audio calls. If secondary microphones (used for noise cancellation) are malfunctioning, recordings may include excessive background noise.

Headphone Connector

Some phones have a 3.5mm connector used for connecting external headsets. When testing the headphone jack, it is important to focus solely on the connector itself, as the speaker and microphone components are part of the external headset. The most common issues are loose connectors, dirt, or poor signal transmission, all of which can degrade audio quality.

Manual vs. automated testing

It is important to note that the human ear perceives audio volume and quality subjectively; what sounds loud or clear to one person might seem quiet or poor to another. This subjectivity makes thorough and objective testing crucial, especially for refurbished devices, to ensure consistent audio quality for all users. When comparing the overall loudness of a speaker manually, the results can vary depending on the person testing, the time of day, their level of fatigue, and other factors.

Manually testing different microphones and speakers can be challenging. For instance, it is often unclear how to record audio using only a specific microphone.

Using robot-assisted testing eliminates these inconsistencies, as each measurement is performed in a repeatable and reproducible manner. For each tested audio resource, including speakers and microphones, the tester performs two audio signal quality measurements and one raw volume level measurement.

The graph below illustrates the loudspeaker volume levels for 100 tested mobile phones of the same model.

This visualization demonstrates how measurement data simplifies the process of comparing and setting thresholds for loudspeaker quality, making the task straightforward and objective.

Similar data is also available for other microphone and speaker measurements, providing valuable insights. As more data is gathered for tested phone models, the testing process can be continuously refined and improved.

With our solution, OptoFidelity FUSION, we provide an automated test system for smartphones that can test the audio quality precisely and detect even tiny variations in the speaker and microphone quality. Speaker and microphone tests are just two of the many test cases of automated test systems for pre-owned smartphones.

Learn more about the capabilities of our FUSION test system for pre-owned smartphones here.

Or contact us now directly to learn more about our offering in the Circular Economy section.