Research & Development

Petrof’s commitment to developing superior instruments stretches back to the company’s birth in 1864, but the company intensified its focus on quality when it established a specialized research centre in the beginning of the 1960s.

Until 1989 the centre engaged in the study of music acoustics for both wind and stringed instruments, but since has only dealt with piano research.

Part of that research includes the study of vibrations, signal analysis, measurement of characteristics of wood and metal and the development of special measuring methods.

In 1995, Petrof opened its free-field room (BM), which is still among the largest and most modern in the Czech Republic.

The company uses the room for acoustic measurements in order to achieve the best possible sound quality of its instruments, ensure their balance and preserving the typical colour of the Petrof sound.
Petrof also allows other companies to use the free-field room under very favourable conditions. These companies need to test the technical parameters of their products so that they comply with the demands of the market and European standards.

Extensive measuring equipment for reading of sound and vibration is available in the room, including means for analysis of signal and experimental modal analysis.

The free-field room has a lower limit frequency of 80 Hz and is not affected by vibrations thanks to its unique design.

The building, which meets the ISO 3745-77 standards, is constructed using the “House in House” method, with barrier-free access.

Its internal parts consist of a reinforced concrete monolith, mounted on springs, with 30cm thick walls that resonate at an approximate frequency of 5.5 Hz and have internal dimensions of 8.6m x 7.1m x 6.6m.

The weight of the monolith, equipped with absorbent wedges 1m long and 24cm x 24cm at the base, is about 300 tons. The absorbent wedges, which are covered with a very thin knitted nylon fabric (silon), are cut to size using a water jet and have a volume density of 100 kg/m3.

The room is equipped with 4180 wedges on walls, ceiling and floor with a total weight of about 15 tons. The net volume of the room, between the edges of the absorbent wedges, is about 160m3.

Besides the wire stepping network, stepping grids are installed from the entry to the centre of the 3m x 2m chamber, which is in the middle of the free-field room.

The grids are removable, allowing for measuring of equipment with a weight over 500 kg. The free-field room entry is 1620mm wide x 1950mm high. Detectors and other electric devices within the room can be interconnected by cables, with measuring equipment situated in the adjacent laboratory.

Petrof also carries out research into the influence of climatic changes on the material features of resonance wood. To this end, an integral part of the research centre are the feutron chambers.
The chambers help with research on the influence of temperature and humidity on building materials and industrial products and influences on biological processes. They also help create stress temperature conditions, and accelerate material aging.

The simulation settings range from - 40°C to more than 100°C, with relative humidity settings available  from 25% to 99% RV.

Timing is automatic with the ability to alternate the temperature differences and humidity levels, and set various air circulation and condensation points.

By being able to simulate different climatic environments through various ranges, the chambers help to reduce the climate risk to instruments once in everyday use.

Temperature and humidity records can be represented in a chart or  timeline, via  the use of a recording thermometer, commeter hygrometer or zapalog, all of which are calibrated.

Records are periodical and have the following error limits: Metrologic class 1 according to ČSN EN 12830, relative humidity error max. ± 1,5% RV, temperature error max. ± 0.3°C.

Data saving rates range from 10 seconds to  24 hours, with a memory capacity of 8000 readings.

Recently, research activity has been focused on cooperation with universities and research centres around the world.

These include the Brno University of Technology, the Technical University in Zvolen, the Czech Technical University in Prague, the Secondary School of Music Instruments and Furniture in Hradec Kralove, the Czech Academy of Performing Arts and the University of Hradec Kralove.
The results gained from academic research is then applied and used in practice.

The most significant example of this successful cooperation is the optimization of the grand piano iron plate. The iron plate used in the new generation of Petrof grand pianos was cast on the basis of results of topological optimization research, using the FEM (finite element method) model of the construction.

Thanks to this method, it is possible to find the points, which are loaded with the highest pressures, tensity or deformation because of both static and dynamic pressures.

Petrof’s research is concentrated on creating numerical models on individual parts of the piano which influence its acoustic features it order to produce an objective assessment of the quality of our production.

For the development of the new upright and grand pianos, the Petrof company uses advanced software to improve the quality of string scaling.

Mensurix 5 Audio is a string scaling software with additional string vibration simulation that determines the contact time of the string with the hammers and each strings volume. Mensurix 5 Audio is also used for the improvement of a strike point line. It is possible to calculate as far out as 9 parameters.

This, and other tools, help Petrof ensure the best quality string scaling, which is one of the most relevant parameters for the quality of the entire instrument and its sound.

Petrof also uses duplexes for longer, richer complex sound.

The speaking length of the piano string is from the capo V bar, or from the agraffe, to a bridge pin. The string vibrates in this section in its fundamental frequency, which determines the tone or pitch.

Along with the fundamental frequency, the string always emits additional higher harmonic partial tones, which influence the tone colour or complexity.

The tone or note, which sounds only in its fundamental frequency, is quite simple, clean, but feels colourless, inexpressive, lifeless and uninteresting.

The tones produced by musical instruments comprised of basic tone and higher complex harmonic tones, to complement the fundamental tone, are rich and make each note sing.

In the range of the high middle and treble section, Petrof lets the string speaking length sound together with its front duplex in front of the capo bar and its rear duplex behind the bridge.

They set these sections using metal frets and these string sections vibrate in harmonic frequencies, which enrich the fundamental tones.

This principle is used in all the new generation of Petrof grand pianos. This results in longer, richer and more complex tones in the higher notes.

Generally, the use of duplex scaling in pianos is demanded by the most discriminating pianists and it is one of the features of advanced piano design used by Petrof in its new grand piano line.