To make sure we meet our required specifications, the Whispr team performed validation testing for sound attenuation, and comfortability, as well as validating electrical functions like live feedback and recording playback.
Whispr’s primary function is to limit the amount of sound that is audible to other people. To verify Whispr’s sound-dampening capabilities, the team ran a physical experiment to determine the level of sound-dampening (dB) provided by the sound-dampening materials as well as the shell units. The target is a 20 dB reduction.
Equipment:
Two phones
One to play music via YouTube
One to measure audio level using the Decibel X app
Foam head test fixture
Whispr mask
Tape measure
Procedure:
Take a tape measure and establish an origin, mark 32 inches away
Open respective apps (youtube, decibel X)
Place the YouTube phone inside of the foam head and place the back of the neck at zero on the ruler
Place the decibel X phone at 32 inches away
Play rainfall audio on YouTube, recording the audio level on decibel X for 30 seconds. Take four measurements
Secure Whispr to the head fixture. Place in the same location and take four more measurements
Take averages for with and without the mask, calculate the difference in dB
Fig. 1. Phone in test fixture
Fig. 2. Head fixture wearing Whispr
As seen in Table 1, with an output of 78.3 dB, the mask reduced the audio level by 17.3 dB. This fell just short of our target of 20 dB. It's important to note that this is an underestimate. Some sound was able to escape through the test fixture because it was made of styrofoam, which impacted the reading when the mask was being worn.
Table 1: Sound Attenuation Results
To test the capabilities of our sound-processing electronics, we performed a yes-no validation test. To do so, we split this test into examining the two functions of the mask: live audio monitoring and audio recording with playback.
Shown below in Figure 3, you can see the audio monitoring validation test. In this test, the user first speaks into the mask, showing what it sounds like without pressing the audio monitoring button. The user then presses the button and speaks again, demonstrating the sound now traveling through the microphone and through the headphones. With this, it was also concluded there was no noticeable delay in the audio monitoring.
Figure 4 demonstrates the validation of audio recording and playback. Before the video started, we recorded a song into the device by placing a phone up to the speaker while pressing the record button. In the video, you can see the user press the play button, resulting in the song being played through the headphones.
Fig. 3. Validation of audio monitoring functionality
Fig. 4. Validation of audio recording and playback
Comfortability Validation
To test the user experience and to validate the comfortability aspect of Whispr, the team performed a user test to gauge the actual lived experience of the user while they engaged in their everyday tasks with the device on. At the end of the test, the user was asked to rate their experience and provide any feedback they might have.
Procedure for Mask Application and Comfort Rating:
First, it was ensured that the mask and IDU are clean and in good condition.
Then, we provided users with clear instructions and any necessary assistance to put on the mask. The following instructions were given.
Hold the mask by the straps with the IDU facing outward.
Place the mask over the nose and mouth, securing the straps around the ears.
Adjust the mask to cover the nose and mouth fully, with the IDU centered on the face.
The IDU should rest comfortably on the bridge of the nose and the upper lip.
Verify that the mask sits securely on the face without causing discomfort.
Once the mask was properly on the user's face, they were taught about the straps and how to adjust them for a personalized fit. The following instructions were given.
Straps should be tightened or loosened as needed for a secure and comfortable fit.
Check that the straps do not cause any undue pressure or discomfort.
Finally, the users were asked to wear the mask for 5 minutes, then rate the comfort of the mask on a scale of 1-10, with 1 being very uncomfortable and 10 being very comfortable. It was emphasized that honest and detailed feedback is essential for product improvement. These comfort ratings were then recorded.
Finally, the participants were asked for additional comments in order to get more specific insight about the comfortability of the mask, as well as how it could be improved.
All data and comments were compiled in the Table E below.
Table E. Comfort Results
Based on the validation, the average rating was 6.5, meaning that the mask was more comfortable than not comfortable. However, given the importance that was placed on comfortability, there is room for improvement, especially with potentially making it lighter and allowing more freedom of jaw movement.
Ultimately, the validation showed that the goals were reached in the design of Whispr, with comfort and sound attenuation as the main priorities.