The base model and final prototype selected for this project is built on top of my own personal shortboard. It is measuring 5 feet 9 inches in length and is made for faster maneuvers like the cutback because of its short length and small volume. Considering these factors the board was selected due to its size and shape, which offer a wider range of motion and faster changes of speed and rotation in comparison to a longboard. Also, the dynamical movement and the internal board vibrations will be different than the one of a longboard or a board with a higher volume. Before the construction, a planning session was conducted with the Noa team to identify the ideal locations for sensor placement, cable routing, mounting of the housing, and material usage considering the exposure to saltwater.
Noa surfboards is a small factory for shaping mostly shortboards and riverboards. With their own shaping studio, they represent one of the few professional shapers in the region of Austria and Germany. This studio was chosen for the professional knowledge and experience of shaping to develop a well-functioning and safe protype.
Looking at the building phase of the protype, Noa Surfboards proposed embedding the piezo disc underneath the front-foot zone of the deck. This area is perfect to capture the movement of the surfer, while not being under strong impact of the bodyweight of the surfer. In order to integrate the microphone in the body of the board a rectangular section of the fiberglass top layer was carefully removed. In the next step the piezo disc was mounted directly to the raw material. To protect the microphone from external impacts and the saltwater multiple layers of fiberglass cloth were laid over the sensor and encapsulate the mic completely.
Another critical technical step was to route the cable from the embedded mic to the waterproof electronics box. Therefore, a narrow channel was drilled on the side of the box for the cable to enter.
Inside the case, the Zoom H4n recorder and x-IMU3 sensor were suspended in a foam block designed to isolate the electronics from board vibrations and strong impacts.
1.1. OVERVIEW OF THE SETUP The hardware setup of this project was developed to function and withstand under the challenging environmental conditions typical for surfing. Therefore, the full equipment needs to not only be made for saltwater exposure, but also be strong enough to handle strong hits and impacts. The sunlight, and hot temperatures also act as another impactor. Therefore, building components were selected based on their stability, mobility, and compactness. The complete system includes a waterproof Pelican 1050 case mounted on the surfboard, containing a Zoom H4n audio recorder, a piezoelectric contact microphone and an x-IMU3 motion sensor. An externally mounted GoPro Hero 3 camera records video and sound. The interior of the Peli case is filed with protective foam to minimize shock and mechanical disturbance. Concluding, the arrangement was optimized to allow a smooth operation during surfing while maintaining robust data acquisition.
1.2. MOTION SENSOR – X-IMU3
The x-IMU3, was developed by x-io Technologies. It is a compact inertial measurement tool (IMU) capable of logging tri-axis accelerometer, gyroscope, magnetometer and orientation data with timestamp precision. For this application, the sensor operated in standalone mode and will be charged by an external small power bank later retrieval. After each recording session, the x-IMU3 GUI and SDK were used to decode. ximu3 binary files into structured CSV datasets (x-io Technologies, 2024). These data streams are then available for the synchronization part with audio and video recordings. Furthermore, these recorded values will be used to manipulate the recorded audio using Pure Data.
The x-IMU3 sensor was selected due to its reliability, sampling rate of up to 500 Hz, and OSC-compatible output structure. This enables later integration with sound synthesis software’s in the later process. The sensor is placed in the box cushioned within protective foam in the Pelican case to minimize noise artifacts caused by board vibration.
1.3. CONTACT MICROPHONE – PIEZO DISC In order to add another dimension to the sound recording by capturing board vibrations and internal mechanical changes, a piezoelectric contact microphone was mounted beneath the surfboard wax layer, at the right side of the nose, near the front foot position. Unlike traditional microphones, piezo elements record vibrations through physical material contact, making them suitable for capturing impactful sound events. Also, due the good implementation movements of the surfer on the board are recorded very well. The sensor is routed to the case using a sealed cable channel and insulation to prevent water from getting in the box or inside the board. This microphone setup allows for the recording of impactful events such as hits, flex, and frictional interactions between the board, the water and the surfer. These signals, together with the recordings of the zoom, form the primary audio source used in the sonic interpretation of the surf session. This implementation of a piezo mic in a surfboard has not been done or documented before and is therefore an innovative approach which is of course interesting for sound engineers, as well as surfers and surfboard builder (Truax, 2001).
1.4. AUDIO RECORDER – ZOOM H4N The audio data was recorded using a Zoom H4n Handy Recorder, configured to capture a mono signal from the contact microphone. The recorder was selected for its portability, sound quality (24-bit/44.1 kHz), and dual XLR/TRS inputs. It was housed inside the Pelican case using closed-cell foam to dampen mechanical noise. Battery-powered operation and SD card storage enabled autonomous recording during mobile sessions. Gain levels were calibrated before each session to preserve signal integrity and prevent clipping. The system was designed to ensure consistent signal acquisition even under dynamic surf conditions (Zoom Corporation, 2023).
1.5. VISUAL SYNCHRONIZATION – GOPRO HERO 3 To also have a video output of the surf session, GoPro Hero 3 camera is mounted at the board’s nose. This video material served as both documentation and reference for synchronization. Here, the synchronization of different audio sources and the sensor data is challenging but will made easier with having audiovisual references. For example, a double tapping on the board can help synchronize image to sound. The GoPro’s audio, while limited in quality, served as another layer reference for alignment. In addition, the video recordings serve also as a tool to analyze body posture, movement patterns, and spatial context (Watkinson, 2013). The surf movie will be consisting of many shots taken by the GoPro and will support the surf film with an immersive camera angle.
1.6. ENCLOSURE AND MOUNTING – PELICAN CASE 1050 The Zoom Recorder, sensor, power bank and cables of the contact microphone are enclosed in a Pelican 1050 Micro Case. This model was selected for its IP67-rated waterproof sealing, shock resistance, and small form, making it not too bulky on the board, but still big enough to fit all the necessary equipment. Moving forward, the case is mounted to the surfboard using strong glue and surfboard wax and is incorporated in the general body of the board. In order to connect the contact microphone from outside to the inside, one hole was made in the box. This hole is again sealed with silicone caulk to make it leak and saltwater proof.
Inside, the box a special Peli foam is inserts to prevent internal motion and a fixation for the sensor and the recorder. The case and cabling configuration underwent field testing, including simulated riding on a surf skate and controlled submersion for a specific amount of time, to ensure no leakage will occur during recording
