Home advantage is built by architects, not by supporters

Decibel readings make good television, but the noise that unsettles a visiting team is mostly a function of the roof above it.

A club puts a noise meter on the big screen and the crowd obliges. It is a nice piece of theatre and it tells you very little, because the number depends far more on where the microphone is and what the stand is made of than on how many people are shouting.

Sound in a stadium behaves like sound in any enclosure. An open bowl with wide gaps at the corners and no roof over the pitch lets energy escape upwards, and the noise that reaches the players is thin and directional. A steep single tier with a low roof overhanging the seats reflects that same energy back down onto the grass, and it arrives as a wall rather than as a direction. Two grounds of identical capacity can feel completely different, and the smaller, tighter, older one usually wins.

Proximity does the rest. Six metres from the touchline and a running track are two different sports for a visiting player. On a track ground the abuse is generalised. On a tight ground it is individual, audible, and aimed, and the difference in what that does to a nineteen-year-old making his debut is not subtle.

Where I think noise actually acts is on the officials rather than on the players, and this is the part that makes people uncomfortable. Players are habituated to crowds by their tenth professional appearance. Referees are making rapid, uncertain, socially exposed judgements under time pressure, and the evidence from crowd-free football was fairly pointed on the direction of the effect. Home teams did not suddenly become worse at scoring. Some of the decision-making gap narrowed.

Which is why the modern stadium worries me a little as an economic object. New builds optimise for sightlines, hospitality volume, catering flow and the ability to host concerts. Those requirements push towards larger, more open, more rectangular boxes with wide concourses and generous distances, and they steadily engineer away the exact features that made the old grounds unpleasant to visit. Clubs then spend money on artificial amplification, drums, and orchestrated singing sections to recreate what the building used to provide for free.

Safe standing has done more for atmosphere in the grounds that adopted it than any amount of pre-match pyrotechnics, precisely because it puts more bodies closer together in a smaller volume of air.

Density beats volume. You cannot buy a low roof after the fact.