Matt Clifford is the keyboardist of Rolling Stones and UEFA anthems, arranger. The Champions League anthem 2012 is one of them, for instance. When he started working for European football, he was coming from world tours with the Stones and he knew perfectly well the acoustics of the stadiums. As he has explained in interviews, there are many parallelisms between concerts and sports events at big venues. The audience, normally tens of thousands of people, evokes intense emotions when shouting or singing. Nobody knows what will happen in an event. There is uncertainty and excitement on each occasion. However, he states that this also happens in concerts since nobody knows which song will be played. When the first chords are played, people vibrate and spread their feelings to all attendants including musicians. Besides, to celebrate both events, the same facilities and sound providers are hired. However, according to Clifford, sports events still have a lot to improve as regards sound, especially now with surrounding sound techniques.  

The audience has always been the prevailing sound at sports events. It is considered player number twelve in the football game. The new stadium designs already take into account and put into practice certain methods to amplify the roar of crowds. This is very important for the team who plays home to be in advantage and intimidate opponents. That is why acoustics in the stadiums has become a key factor. In fact, it is a vital ingredient in all sports. In basketball, it is key to have silence when the team who plays home attacks and deafening noise when the one who plays away does it. This was proven during the pandemic when games were played without audiences, many live broadcasts added a background effect that seemed to be the fans’ noise created by sophisticated systems. 

Despite this, more and more stadiums face obsolete acoustics problems. If facilities are obsolete, loudspeaker sound might be deafening and even harmful. Global Sport Matters warned that the bearable decibels were sometimes exceeded in many NBA games and that there was a risk of minor but permanent injures for players and the stadium staff. According to a study mentioned, half of the referees suffered from tinnitus (ringing in the ears). However, the demands of modern shows do not stop. It is even higher and higher and this implies the incorporation of effects that needs high audio volume either of the speakers, the videos on the screens, or Augmented Reality. A mid-range stadium as Molineux, home ground of the English Wolverhampton, had to install a new audio system so as all the activities planned for the game-day such as interviews with players and experts and even a fireworks show could be carried out.

Under these circumstances, the science of sound at stadiums has greater demand and complexity than it seems to have at the beginning. The loudspeaker system and videos should get to all seats with the same intensity. Voice of attendees, at the same time,  should have enough volume to get people excited and to be part of that collective catharsis that, in the end, is what makes fans come back to the stadium instead of watching the game from the comfort of their houses. The problem is that the bigger the premises, the more difficult it is for the sound to reach all parts in the same way. 

Currently, most of the biggest European stadiums have partial roofs which make sound waves rebound inwards.  In the past, stadiums were open and that made the sound “escape” out. One of the experiences that made this problem evident was probably the Tokyo 1964 Olympic Games. Yoyogi National Stadium had important acoustic problems due to its wide roof designed by the architect Kenzo Tange. Consequently, Los Angeles 84 Games pioneered acoustical simulations.  An essential technique in this field. 

New stadiums focus on acoustics

A significant example of this was the construction of Tottenham Hotspur new stadium. Its president, Daniel Levy wanted the new premise to be even noisier than the previous one, which was already famous in England for its environment. Acoustics was considered from the beginning of its design and in order to carry the project out, they hired Vanguardia, the company that was in charge of U2’s sound, for instance. By using a spectrogram, a tool for making a visual representation of the sound, they created a series of graphs that showed in detail how the sound waves would move around the stadium, how they would rebound on different surfaces and materials, and how they would get to all parts of the building. With that information, the angles of the roof panels were adjusted and the proper materials were chosen to maximize the audience’s shouts. 

However, the key reference was given by the observation of the field. After traveling around Europe analyzing the most important premises, the technicians in charge of the new Spurs stadium observed that the stadiums with the best atmosphere all share a common detail: they had large areas of seats without free spaces where the noisiest fans were located. Thus, in Tottenham, architects placed all the premium facilities on the east and west stands, and the general locations were concentrated on the north and south ones. In fact, its south stand is the biggest in all the UK with seats for 17500 spectators and a special design focused on sound. It has a 35-degree inclination and a slight elevation that together with the panels placed on the lower part of that area of the field was specially designed to project a “wall of sound” in the games. It is an architectural loudspeaker. 

The effects of sound in and out of the stadium 

On the other hand, the sound that gets out of the stadium must be taken into account when thinking about the relationship between the stadium and the urban, natural, and neighborhood environment in which it is located. Basically, the environment cannot be acoustically affected, high sound levels must only be effective inside the premises. This problem has already been detected in the USA while modernizing stadiums since their activities ended up having an impact on the surrounding residential areas. Meteorology must be added to the list too. When analyzing the development of the last stadiums built in Europe, Slaski in Poland is considered to be an interesting example. There many concerts of bands with high demands as regards decibels such as Iron Maiden or AC/DC were held.  When the new sound system was installed in 2009 what was seriously taken into account was the adverse weather conditions in winter in Poland. The higher the humidity, the more probable the refraction. It is the same the other way round, the higher the temperature, the faster the sound moves. If the air is hot near the ground, the waves will tend to move upwards and the sound will have less intensity.

Chairs are considered to be another problem for acoustics in stadiums. They are normally plastic ones because they are cheaper and easier to maintain, but when there are no spectators to absorb the sound, reverberation is uncontrollable. Empty seats cause sound distortion. 

According to Ken Voss, an engineer at RCF USA, in a sports event, the audience gets, on average, a sound ranging from 85 to 90 decibels. When there is a dangerous play, it may increase up to 110 and 115. In the USA, the registered record is 142 decibels in Arrowhead stadium in Kansas City. In European football, the noisiest games reached 113 decibels in Anfield Road, Liverpool or 111 in San Siro, Milan.
Under these conditions, the audio transmission must exceed in at least six decibels the audience sound, Voss explains. However, this only happens “in an ideal world”. Sound should keep that margin and must be audible. However, it will encounter the problems mentioned before. And the issue is that, apart from being used for entertainment and advertising, loudspeakers transmit relevant information in case of evacuation or any type of safety issue.  There are clear regulations about the intelligibility of messages stated by the UEFA and FIFA. 

More and more ideas and interesting solutions are coming up in the USA to offer a 100% positive experience and comply with the safety regulations. Transmissions that can be synchronized from each seat of the stadium are becoming more common. For instance, Mixhalo app, launched by Mike Einziger, Incubus guitarist, allows users to play the TV broadcasts. His idea was born based on the fact that the loudspeaker systems at stadiums will never work properly due to the environmental sound. With this app, the external noise is blocked and the spectator can focus on what they want to hear. In football, listening to the sound of the crowd may be as important as listening to the sounds recorded on the grass or the speaker’s animation.  This technology was already implemented by Buffalo Sabres in the NHL, and Sacramento Kings in the NBA. The original idea was born in rock concerts. Sting, Aerosmith, and Metallica have already implemented this so their spectators do not listen to the rest of the audience and can just listen to the band, but, at the same time, do not dispense with the emotion of thousands of people. 

On the other hand, if perfect equalization is aimed at, there are other ideas coming from the world of rock music. Alistair Jame, who played with the ex-Guns N’Roses drummer in many tours, together with Raymond McGlamery has created Audion, an app used to modulate the loudspeaker sound in every location of a stadium. This system is installed at Yankee Stadium in New York. What is taken for granted here is the progressive deterioration of the loudspeaker system. This is inevitable and, when it happens, the normal trend is to turn up the volume, and this results in broadcasting or hearing issues experienced by a part of the audience or at different areas of the stadium. Audion enables the separation of each sound coming from screens, music, or the speakers, and the intelligent adaptation of the broadcast to each need and situation. Currently, the new business need of sports clubs is attracting music artists to play at their stadiums. Experiencing rock concerts is the best way to learn and improve in this regard.