Hit songs are getting louder and rhythmically more repetitive, according to a scientific study of chart music, which concludes that pop's golden era was actually the often-maligned 1980s.

A research team from the University of Bristol's Intelligent Systems Laboratory in the Faculty of Engineering set out to predict the popularity of a song by using state-of-the-art machine learning algorithms.

The team examined the UK Top 40 Singles Chart over the past 50 years and sought to identify the distinguishing features of songs which made the top five, compared to those which stumbled outside the top 30.

The researchers used musical features such as tempo, time signature, song duration and loudness. They also computed detailed summaries of the songs such as harmonic simplicity, how simple the chord sequence is, and "non-harmonicity" – how "noisy" a song is.

By weighting the most significant 23 audio features, the team, led by Dr Tijl de Bie, produced a catchy equation for a potential hit: (w1 x f1) + (w2 X f2) + ... + (w23 X f23). How good is this equation? They claim it can predict with an accuracy of 60 per cent if a song will make it to the top 5, or if it will never reach above position 30 on the UK Top 40 Singles Chart.

The team discovered several trends which may explain why the singles chart, dominated today by R&B/dance collaborations, has been described as the least diverse it has ever been.

Before the Eighties, the danceability of a song was not very relevant to its hit potential. But following the disco boom in the late Seventies, danceable songs were more likely to become a hit.

In the Eighties, slower musical styles (tempo 70-89 beats per minute), such as ballads, were also more likely to become a hit than now. The UK's best-selling singles of 1985 were "slowies" – "The Power Of Love" by Jennifer Rush followed by "I Know Him So Well", the Elaine Paige and Barbara Dickson duet.

The researchers found it most difficult to "predict" hits around 1980, when the charts were in a state of ferment following the punk explosion. Bands like Depeche Mode experimented with synthesisers, while rock bands The Jam and The Police co-existed in the top 10 with disco, soul and reggae songs. A new wave of colourful pop acts led by Adam and the Ants and Duran Duran was also about to emerge.

Although the early Eighties are often dismissed as a time of tinny, vacuous music, the researchers argue that "the late Seventies and early Eighties were particularly creative and innovative periods of pop music".

Hits changed in the Nineties as the "simpler, binary, rhythms such as 4/4 time", the mechanised DNA of House music, became dominant. Cheaper technology meant that anyone could construct a hit record in their bedroom. Yet it appears that your dad was right all along – pop music is getting noisier. "On average all songs on the chart are becoming louder," the team found. "Additionally, the hits are relatively louder than the songs that dangle at the bottom of the charts, reflected by a strong weight for the loudness feature."

Producers tweak songs so that they "cut through" on the radio and club sound systems, using a variety of techniques. The sound is compressed, enhancing the bass end "thud" and punchy female choruses of chart-aimed songs.

Dr De Bie, senior lecturer in artificial intelligence, said: "Musical tastes evolve, which means our 'hit potential equation' needs to evolve as well. Indeed, we have found the hit potential of a song depends on the era. This may be due to the varying dominant music style, culture and environment." That is why they worked out the hit potential equation as a function of time. This shows what is important in each given era, and the evolving priorities of fans.

Music experts however posit an alternative equation for a chart cert today – The X Factor. The songs colonising the current top 10 are those created by the talent show or by artists who performed in the sought-after guest slots, watched by millions of potential record-buyers. Coldplay's sales soared 132 per cent this week after their appearance during the series final.

The pop equation is explained at: scoreahit.com/TheHitEquation

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