a-SHOE-stics
A research project into the sonic acoustics of performance basketball shoes
By Shaun Gardiner
Published 2021
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The NBA tipped off its diamond anniversary 75th season on October 20th 2021 with a doubleheader: the reigning champion Milwaukee Bucks played against title favourites Brooklyn Nets, and a new look LA Lakers side squared up against a revamped Golden State Warriors team. The start of the new season doesn’t just bring the return of basketball to our TV’s, but it also brings the dawn of new basketball shoe releases for the season. The season opener alone gave us previews of the Curry Flow 9, Nike Lebron 19, and Nike Zoom Freak 3 models, of which only the Zoom Freak 3 is available now.
With NBA basketball as popular as ever, the market and demand for performance basketball shoes have also peaked thanks to the promotion and marketing not only from companies but also from high-performance athletes within the sport. The game of basketball is constantly changing and adapting, and so is the footwear, with materials and technology becoming more advanced, more lightweight, and more durable than ever before to give athletes an edge.
Not so similarly, advances within the creative music industry have also been taking place. Now more than ever, producers, engineers and artists are finding new ways to record music and manipulate sound. By experimenting with microphone placement and the use of objects (among many other things) we’ve discovered many different unconventional recording techniques, all with varying results.
Despite the research and experimentation done within the world of creative music, no one has ever thought to make a connection between the two fields of music and shoes and use the materials on performance basketball shoes in music-making, especially given that the shoes’ materials are often premium and potentially offer a lot of possibilities within the unconventional recording landscape.
This research project aims to investigate the relationship between music and shoes, discover the sonic acoustics of the materials found on some of these performance basketball shoes and answer the question “How does the technology and materials used on performance basketball shoes affect sound?”
I discovered my love for shoes when I was researching indoor court shoes to wear for Ultimate Frisbee, something I love just as much as shoes. The culture and community around sneakers are awesome, and there’s something about what you put on your feet that can bring out your confidence and character, in addition to the “swagger” that comes with wearing cool shoes that makes me love them so much. I opted to search for basketball shoes due to similarities with the speed of both basketball and ultimate frisbee, as quick changes of possession can result in the game quickly stopping and starting. I had a general idea as to what made a “good” basketball shoe thanks to my experience working in retail at New Balance, an experience I admit fuelled my love for shoes even more. Working at New Balance, I’ve been able to witness first-hand the company’s drive and desire to provide quality shoes and interesting shoe technology to its customers, and I’ve always found it interesting as to what goes into making these certain technologies and the materials that are used in creating New Balance running shoes.
‘a-SHOE-stics’ originally started as a note on a Google document. It simply said “Shoes?” The note was for a music project pre-production course, a way of kickstarting ideas and thinking of things that could be done for a major project. It was far and away my weakest idea, that was until my mate Richard gave me the idea to experiment using shoes in an unconventional recording environment. That recommendation was what got the gears moving and sparked the start of this project, my interest and passion for shoes took care of the rest.
Thanks, Richard <3
I took inspiration for this project from unconventional recording techniques and out of the box ideas, primarily those used by YouTube content creators Sylvia Massy and Creative Sound Lab who break the boundaries of conventional recording.
Creative Sound Lab’s videos include recording tips and tricks in addition to creating outside the box recording. Two videos that caught my interest and inspired me were around using a garden hose and trash cans to create drum reverb. I’ll admit, I didn’t expect much, but I was really blown away with the sounds Creative Sound Lab was able to get using those everyday items, and even more blown away when he combined those sounds with a compressor.
Sylvia Massy describes her style as “Adventure Recording”, which is exactly what she does. Going above and beyond studio recording, she’s recorded inside of nuclear cooling towers and in train tube stations to name a few places. Both of those locations produced ridiculous and awesome sounding reverbs, it was incredible. Her work inside of the recording studio is impressive too, with one video showing her recording drums through a $5 cassette tape, which also produced some impressive sounds.
These inspirations and examples gave me hope that what I was about to do could achieve or produce similar results and made me excited for the future of ‘a-SHOE-stics’.
Links to the above channels:
Sylvia Massy – https://www.youtube.com/c/SylviaMassyKnowsStuff/featured
Creative Sound Lab - https://www.youtube.com/channel/UCSCwzZX29jTILlsP4MhjQvg
So how do the materials on performance basketball shoes affect sound? To understand and answer that, we first need to know what materials we’re dealing with, which means it’s time to introduce the shoes!
For clarity, my interpretation and definition of a “performance basketball shoe” is a shoe that performs to a high standard when used in a basketball environment, usually an indoor hardwood floor. Often seen in the NBA or similar, these models can withstand the intensity of the game time and time again and are often equipped with technology to give the wearer an advantage. Additionally, these shoes need to be widely available to the market at the time the research took place.
For consistency with the testing, all the shoes I tested are the same size (US 8) and are a low top, meaning the upper doesn’t sit above your heel, and all recordings were done using the right foot of the shoe.
Introducing first is the Curry Flow 8. The new Curry brand is named after All-Star Point Guard Steph Curry. It is owned by Under Armour, a brand that Curry has worked with for seven different signature shoe releases up to this point. Released on December 11th 2019, these shoes are extremely lightweight, mostly thanks to the lack of rubber on the shoe which is said to eliminate roughly 85 grams of weight. The midsole and outsole are a one-piece, all foam construction that features Under Armour Flow cushioning technology, which was originally intended for runners only until it was tested on indoor hardwood flooring where they discovered it gripped extremely well and was perfect basketball. Within the midsole, a “Pebax” plate can be found, which is a Thermoplastic Elastomer Plate. It is used to provide more bounce and cushioning to your steps. The upper consists of a tight, two-layer, flat knit and woven material. The knitted material allows the foot to breathe while also being extremely lightweight with a sock-like fit. Synthetic leather panels on the sides of the upper help to provide additional support when moving laterally. It is a one-piece upper, or “Bootie” upper, which means there is no tongue on the shoe. All together the shoe weights a total of 345g.
Steph Curry wearing the Curry Flow 8 "Feel Good Flow". Source NBAKicks / Twitter.
Secondly is the Puma All-Pro Clyde, the newest shoe in the ever-growing “Clyde” line of footwear which continues to honour Hall of Famer Walt “Clyde” Frazier. This sleek performance basketball shoe was released on November 11th 2019, and sports a ProFoam+ midsole with EVA technology for added cushioning and response. EVA stands for Ethylene Vinyl Acetate, it is an engineered plastic adhesive with rubber-like properties while also being significantly lighter than real rubber by roughly 40 to 60%. Speaking of rubber, the outsole is covered in a thick, high abrasion-resistant rubber which provides great grip and easy changes in direction. A Pebax plate is also featured in this shoe. A tightly woven textile upper features Matryx Evo Tech: a lightweight, breathable, flexible, supportive and adaptable upper technology which features high tenacity synthetic yarns made from polyester. The upper is coated with polyurethane and technical yarns, and also features carbon zoning in high-stress areas to help maintain support. The Puma is the only shoe in the sample group which features a tongue. This tongue is heavily padded and thick, made from cotton-like material. This shoe weighs in at 340g.
LaMelo Ball rocks the Puma All-Pro Clyde. Source USAToday.
Lastly is the New Balance Omn1s Low. Having not made a basketball shoe since the ’90s, New Balance is back and ready to re-establish itself in the scene. The Omn1s, which was released originally in high top form on October 23rd 2019, was well received by customers. The low tops were released almost a year later on July 30th 2020. It features a Fuelcell midsole cushion setup, which is infused with nitrogen and carbon dioxide to provide greater bounce and energy return. A Pebax plate features once again, and a hard blown rubber outsole provides plenty of grip. In between the midsole and outsole is a TPU (thermoplastic polyurethane) beam shaped like a chicken foot, which provides torsional control in the midfoot and an extra spring in your step. The upper features both a loose-knit “tongue“ piece and tight-knit textile labelled “Fitweave”, despite being a bootie style upper. Fitweave is a multi-layered jacquard upper made from plastic and fuse textile. It is tight, tough, heavy and durable. The heel of the shoe features a heel counter to support the rear of the foot and is designed to hug the heel and stop any slipping. A synthetic leather heel cup comes across near the ankle of the shoe and an elastic band helps provide a bit more support in the midfoot. The Omn1s are the heaviest of the three shoes, weighing 360g.
Darius Bazley practising in the New Balance Omn1s Low. Source Bleacher Report Kicks / Twitter.
To test the materials on the shoes, a decision needed to be made as to what the best recording process would be. The first tests for the project involved microphone placement with the shoes, trying out different microphones and seeing what worked and what didn’t.
There were four microphone placements: inside the shoe facing the upper, inside the shoe again but facing the outsole, outside the shoe with the microphone pointing into the insole, and lastly, outside the shoe facing the outsole. It was quickly discovered that using a dynamic microphone wasn’t the most practical, like a Shure SM58, as the diaphragm often pointed up at the top of the microphone which made it hard to angle and get sound travelling through the materials, it was only viable when using it to point into the insole of the shoe. Condenser microphones, like the Behringer C3, had diaphragms facing the sides of the mic head, and their shape allowed us to easily get the microphones around the shoe and pointed at the materials. The shoe used for this testing was the New Balance Fresh Foam Tempo, a lightweight running shoe.
Researching was done into suitable microphones for the recordings. A microphone with a long and flat frequency response was the most ideal for the project to give us the best and most even readings. I chose microphones that were suitable for vocals (according to Massey University’s microphone booking system) as recording with vocals was likely the most viable use of this unconventional recording technique. Five microphones were chosen: the Rode NT-1000 and Behringer C3 were condenser microphones, and the Sennheiser 421, Shure SM58 and SM57 microphones were dynamic. All the microphones had cardioid polar patterns, meaning no sound or sound reflections would be collected from the rear of the microphone.
Frequency Response of the Shure SM58. Source Shure.
Frequency Response of the Shure SM57. Source Shure.
Frequency Response of the Sennheiser 421. Source Sennheiser.
Frequency Response of the Behringer C3. Source Behringer.
Frequency Response of the Rode NT1000. Source Rode.
Of the four microphone placements, having the microphone inside the shoe facing both the upper and outsole was the most practical. The shoe essentially acted as a filter for the microphone and allowed us to easily speak, sing and put sound through the materials and into the microphone. When it came to microphone choice, I opted for the Rode NT1000 not only due to its practicality with the recording technique but because I believe it captured the clearest and brightest sound, largely thanks to its 1” diaphragm.
Using this technique and the Rode NT-1000, it was time for the final testing. To test the sonic acoustics of the shoe materials, I would use a white noise generator coming from a laptop, through a speaker, through the materials and into the microphone. Both the upper and outsole shoe materials would be tested to compare how much the sonic acoustics vary from each side of the shoe in addition to the response of the other shoes. The speaker of choice is a Genelec 825A DSP Bi-Amplified Monitoring System (50/60Hz and 170W for those who are interested), a recording studio quality speaker used often around the Massey University Campus. White noise will be playing at 85db at a distance of 1.2m away from the shoe.
I hypothesise that lighter weight materials will allow for a greater frequency response because less material for sound to travel through should result in more sound coming through. Because of the chosen materials and lack of rubber on the Curry Flow 8, I believe the material on this shoe will give off the widest frequency response.
Hearing the audio side by side for the first time, it was interesting listening to the audio produced by the materials of each shoe. The Curry Flow 8 gave off the widest frequency response of the three when travelling through the material on both sides of the shoe, and also gave us the brightest sound of the three too. One shoe which surprised me was the Puma All-Pro Clyde, with both sides of the shoes’ materials providing low-frequency responses despite the sleek midsole and overall weight of the shoe. The New Balance Omn1s had similar characteristics to the sound from the Puma All-Pro Clyde but offered a brighter sound than that of the Puma despite being roughly 20 grams heavier.
Using a piece of software called Sonic Visualiser, I’ll be able to better see what frequencies are being affected to identify the material’s sonic characteristics.
As mentioned before, the Curry Flow 8 had the widest frequency response of the tested shoes, and these graphs prove that. I believe a lot of it has to do with the weight of the shoe and the lack of rubber to absorb sound.
The upper material picks up a lot of high-end frequencies and gets very busy and bunches around the 4k-8kHz mark. There’s also a dropoff around 150Hz and a peak at 1kHz. This knit material is pretty stretchy, which could allow higher-end frequencies to pass through easier.
The foam outsole also did a good job collecting a range of frequencies too, ranging from 40Hz to 2kHz, with some bunching frequencies around 1kHz. The drop at 150Hz stays consistent with the upper.
The Puma All-Pro Clyde was the biggest surprise to me, as this was a shoe I thought would collect frequencies just as widely as the Curry Flow 8 did. It makes me wonder whether the materials on the Puma would be more durable because of the narrow frequency response.
The upper peaked plenty in the low to low-mid frequency range before dropping off and bunching up between 800Hz and 2.7kHz, where it eventually dies off. Despite the range, the audio is mostly dominated by lower-end frequencies, something I find very interesting and could be caused due to the construction of the upper.
The outsole, despite being one of the slimmest in the group, only allowed frequencies of up to 800Hz before completely dying off. As a result, the audio is deep and very drowned out. This response might be a result of the cushioning within the midsole and the thick rubber of the outsole affecting and absorbing sound.
The New Balance Omn1s frequency response is very similar to that of the Puma All-Pro Clyde, the frequency range and response is essentially the same. The audio is extremely similar too, with the Omn1s being a little brighter and having a little bit more mid-range with the upper material. The outsole response, however, is almost identical, with the only difference being the Omn1s was a bit louder. They even have the same frequency cut off point at 800Hz.
Maybe the materials and technology on these two shoes aren’t so different after all?
The varying frequency responses using this unconventional recording technique allow for many creative applications, and could even help reduce the need for some plugins during post-production mixing and mastering. With that in mind, I headed back into the studio to try some creative applications of my own.
Firstly, I mic’d up a kick drum with an AKG D112 and a snare drum using a Shure SM57. I covered the diaphragm of the kick mic with the outsole of the Puma All-Pro Clyde (and held the shoe in place using tape) and positioned it just outside the cover of the bass drum to accommodate for the shoe, and angled the SM57 so that it collected the frequencies of the snare drum through the upper of the New Balance Omn1s. The result was a very lo-fi sounding drum kit which sounds awesome.
I opted for a single overhead microphone for the recording of the piano. An AKG C-451 pencil mic was positioned over the piano and covered with the knit material of the Curry Flow 8. A small piece of tape was used to hold the shoe in place as it dangled over the piano. I think the piano would have benefitted from another microphone and placing those microphones on either side of the piano instead of having one in the middle, but overall I thought it came out well.
Thanks for shredding the keys for me, Nicole!
Last up was vocals. I opted to use the Curry Flow 8 upper again for this test because it was the one with the widest frequency response. I called upon my good mate Hugo to rap into the shoe. The result was as I expected it to be, a nice wide frequency response, loud, and clear vocals. I was surprised at how well the materials did keeping out “pop” and “hissing” sounds. The materials on the shoe essentially acted as a pop filter here which was an interesting discovery.
To conclude, this research project aimed to discover the sonic acoustics and characteristics of the materials used on performance basketball shoes and answer the question “How does the technology and materials used on performance basketball shoes affect sound?”, which I believe I have answered. This project has helped contribute to sound engineering practices by demonstrating and displaying the sonic characteristics and the frequency responses of the materials on these shoes and provided an insight into the potential of using performance basketball shoes within studio music recording. There are so many shoes and so many different possibilities and potential sound profiles yet to discover with music recording. I hope this work shows the untapped potential of this unconventional recording technique and opens the door for shoes to be used more in recording studios, among many other things.
A huge thank you to Dr Jon He for mentoring and assisting me with this project. Your continued support and belief in me and the outcome of the project helped get ‘a-SHOE-stics’ to where it is now.