During the Winter Olympics which was held in Beijing in 2022, the spotlight was constantly on the athletes and their exceptional performances. People from all over the world were watching the competitions either television or the Internet. Other than sporting achievements, the spectators would also appreciated when the commentators provided some clearly understandable and interesting explanations.
In fact, the loudspeaker announcements are an important source of information for both athletes and spectators at different venues. It is completely evident that at a highly important international event such as Winter Olympics, the expectation is that loudspeaker announcements be easily understandable for everyone.
In addition, the sound quality in the commentary rooms, lounges, broadcast booths and hallways is important. That is why, acoustics experts have trusted NTi Audio acoustic equipment since the start of the construction and renovation of event venues, such as the Water Cube.
Therefore, from the very beginning of the construction to the end of the project, acoustics consultants monitor every step of the process to make sure that all acoustic specifications were fulfilled and to the best possible sound quality and sound clarity.
For evaluating announcement quality, subjective listening alone is not enough to judge the final quality. In fact, objective measurement of the STI or Speech Transmission Index is the scientifically-accepted technique.
The GB/T 28049 standard Code for sound reinforcement system design of stadium, gymnasiums and auditoriums sets
auditorium, gymnasiums and stadium sets distinct requirements for the STI (speech transmission index) (STIPA for PA systems) in stadiums.
Firstly: Reverberation Time
One of the key criteria for speech intelligibility is reverberation time. Many people have experienced live announcements or commentary in a highly reverberant indoor space.
The effect of reverberation on speech intelligibility is shown in the two audio clips below:
The requirements for a sound reinforcement system are direct consequences of the reverberation time and room volume. A carefully measured and well planned sound reinforcement system can guarantee a high speed intelligibility for a room having a volume of 80000-160000 m³ and a reverberation time of 1.6-1.8 s.
It is important tp note that there is a clear distinction between arenas and stadiums, as a closed arena produces more like a diffuse-field conditions, while an open stadium produces more like a free-field.
It is not an easy task to measure reverberation time in a large arena. It needs not only easy-to-operate and precision instrument, but also a powerful sound source which can fill up the room with the test signal. This is where the lightweight DS3 Dodecahedron Speaker Set can play an important role.
The results of the measurements will be read directly on the XL2 Audio and Acoustic Analyzer. This way you can immediately identify the areas that do not fulfill the requirements. Since there is no no post-processing of data, the time required to carry out the procedure is immensely reduced.
The ambient noise is inversely proportional to the signal-to-noise ratio. It means that the louder the ambient noise, the less intelligible announcements are: so far so good!
The point is that, spectators’ noise is not the only influencing factor. Therefore, acoustics consultants evaluate the venue when it is both full and empty. There is no noise from spectators when the arena is empty, but there are other noise sources such as lighting, air conditioning and ventilation systems. This is where noise curve measurements play an important role. In fact, it is quite easy to measure noise curves. They can be easily measured and read from the XL2 Audio and Acoustic Analyzer which removes the need to to cross-reference the frequency spectrum. The GB/T 28049 standard total sound level of NR35 at maximum.
It has always been difficult to identify that how far ambient noise can influence speech intelligibility. Basically, it is due to the fact that playing a powerful test signal and making loads of measurements in the middle of the watchers is sort of impossible.
To resolve this dilemma, NTi Audio has introduced a creative feature to correct the influence of ambient noise. Firstly, the acoustic consultants measure the speech transmission index STIPA in a vacant arena, afterwards overlay the result with the level of ambient noise recorded when the arena is full with spectators.
In other words, first the speech transmission index (STI) is obtained in the presence of the spectators, and then the contradiction between actual measurement and theoretical requirements is resolved.
Sound Pressure Level
It is difficult to hear whispers, and we all agree that the louder the sound, the better you can hear it. In fact, scientists used to think this way as well. But people cover their ears when the sound is too loud!
After many years of experimentation and research, it was discovered that you can achieve the best speech intelligibility when the sound pressure level is between 60 and 80 dBA.
There is more!
There are many more acoustic considerations such as noise pollution and sound insulation which must be considered in their entirety. Thanks to the efforts of all acousticians who carried out sophisticated measurements that did their best we could ultimately enjoy many great events!
At last, Felixtrument supplies a complete range of innovative acoustics, audio and vibration equipment which come in different types and sizes. Therefore, if you are in need of any Sound and Vibration equipment; you may browse through our various products which you may find in the mentioned link; to find the one which best suits your needs.