Building acoustics describes the interplay of sound generation, sound propagation, and noise control in and on structures. In the context of concrete demolition, special demolition, rock excavation, and tunnel construction, it takes on particular importance: here, hard, often strongly coupled materials such as concrete, reinforced concrete, or natural stone meet tools applying high forces. For practical work this means: airborne sound, structure-borne sound, and vibrations must be planned and controlled—especially when working in existing structures, when sensitive neighborhoods are affected, or when uses such as hospitals, offices, schools, or production facilities continue to operate. The products and application areas of Darda GmbH are exemplary of methods that can be performed with hydraulic, predominantly static techniques to reduce noise and vibration exposure and to purposefully improve noise control during the construction process.
Definition: What is meant by building acoustics
Building acoustics is the study of sound in construction. It encompasses the generation of noise (sound sources), transmission through air and building components (propagation paths), and the effects on people and sensitive facilities (receivers). Key quantities are sound pressure level in dB, frequency distribution, and time weighting (e.g., equivalent continuous level). In deconstruction, vibrations and the resulting vibration velocity in building elements are also decisive. Building acoustics consistently considers the source–path–receiver triangle and translates it into protective measures such as method selection, shielding, decoupling, pacing, and monitoring.
Fundamentals of sound propagation in buildings
Sound propagates as airborne sound and as structure-borne sound. In existing structures, components such as slabs, walls, columns, and foundations are efficient conductors of structure-borne vibrations. Steel reinforcement, rigid joints, and closed rings facilitate transmission. At interfaces there may be decoupling or—under unfavorable support conditions—amplification. Particularly relevant are resonances (frequency-dependent amplifications) that result from material stiffness, mass, and damping. Concrete exhibits high sound conductivity for low-frequency components; porous layers or elastic bearings increase damping. For site practice the rule is: the more impulsive and harder the excitation, the higher the risk of high peak levels and widely propagating vibrations.
Airborne sound and structure-borne sound in deconstruction
Airborne sound arises from direct radiation at the source (e.g., drives, fans, friction and fracture noise). Structure-borne sound is generated by mechanical coupling between tool and component. Point-like, impact-type excitation (hammering, chiseling) produces high peak sound pressures and relevant vibrations. Static, hydraulic methods such as splitting or crushing with jaws excite the component much more softly and shift energy content to lower frequencies that are often easier to control at the point of work. For example, crushing with concrete crushers can be used to minimize impulsive excitation.
Frequencies and perception
High frequencies are easier to shield; low frequencies penetrate components and travel long distances. Fans on hydraulic power packs often generate mid- to high-frequency content, crack propagation in concrete tends to produce mid frequencies, while structural vibrations are mostly in the low-frequency range. For residents and users, continuity, recurrence, and peak levels are crucial—not just the average. Building acoustics therefore targets the reduction of impulses, limitation of low-frequency excitation, and balancing of steady-running noise sources.
Sound sources in concrete demolition and special demolition
Typical sound sources include the interaction between tool and component, auxiliary equipment, material handling, and secondary noises (falling components, friction, separation). Methods differ significantly in their acoustic signatures:
Concrete pulverizers in structured deconstruction
Concrete pulverizers work with high but steadily increasing forces. The result is a predominantly quasi-static excitation of the component. Impulses can be limited if cycles are run uniformly. The demolition edge can be defined by pre-scoring or pre-drilling to avoid uncontrolled spalling. For building acoustics this means: lower peak levels, reduced structure-borne input, and good controllability in sensitive environments such as strip-out and cutting in existing structures.
Rock and concrete splitters in sensitive zones
Rock and concrete splitters build up stresses in the component until a crack propagates in a controlled manner. The actual separation takes place without impact work, which significantly reduces airborne sound and vibrations compared with percussive methods. Combined with forward-looking cut planning, massive elements can be divided into transportable segments—advantageous for work in the immediate vicinity of sensitive uses or during night work windows.
Hydraulic power packs and drives
Hydraulic power packs (hydraulic power units) cause airborne sound (engine, fans, flow noise) and can inject structure-borne sound if they stand rigidly on load-bearing plates. Acoustically favorable are elastic bearings, vibration dampers, low-turbulence line routing, demand-driven speed control, and shielding of direct sound paths. Location choice and fan radiation direction have a major influence on immission levels.
Combination shears, multi cutters, steel shears, tank cutters
Cutting methods generally generate less low-frequency vibration than impact tools. With thick sections and high-strength steels, however, local cracking noises may occur. With tank cutters, the cavity plays a role: resonances can be limited through cut planning, openings for pressure and acoustic decoupling, and sound-absorbing inserts. Multi cutters and steel shears benefit acoustically from smooth feed strategies and uniform pressure ramps.
Acoustically informed planning of deconstruction, strip-out, and cutting
Acoustics starts before the first cut. Systematic planning lowers emissions, increases execution quality, and improves acceptance. The focus is on selecting suitable methods (e.g., concrete pulverizers, rock and concrete splitters), sequencing the work steps, and shaping the propagation paths.
- Survey of existing conditions: material build-up, component thicknesses, supports, possible resonance paths, surrounding uses.
- Forecast: expected airborne sound and vibration levels, especially for low frequencies and impulses.
- Method selection: prefer hydraulically static separating methods; limit percussive work to the technical minimum.
- Pre-processing: saw cuts, scoring, or drilling to guide cracks and reduce uncontrolled spalling.
- Sequencing: smaller partial cross-sections, uniform cycle pacing, selection of acoustically favorable operating strokes.
- Decoupling: elastic bearings for power packs, decoupled work platforms, rubberized interlayers at contact points.
- Shielding: mobile noise barriers, mass-plus-absorber combinations at reflective surfaces, oriented placement.
- Logistics: quiet transport routes, damped rigging, controlled placement of segments instead of dropping.
- Monitoring: targeted use of measurements to steer site acoustics in real time.
Interfaces with structural engineering and MEP
Acoustic measures must be coordinated with structural engineering, site setup, and building services. Decoupling must not cause inadmissible settlements or instabilities. Air routing, exhaust, and cooling of hydraulic power packs must be planned so that acoustically favorable flow paths result.
Metrics, assessment, and documentation
For assessment, A-weighted sound pressure levels, maximum short-term values, and spectral analyses are used, among others. For vibrations, vibration velocity is decisive, often frequency-weighted and component-oriented. Effective are traceable measurement concepts, reference measurements before construction starts, and continuous documentation during the work.
Practical monitoring
Measurement points should map the essential paths: near the source, along structural paths (slabs, walls, stair cores), and at sensitive areas. Geophones for structure-borne sound and microphones for airborne sound complement each other. Weather, wind, and extraneous noise must be considered. Evaluation in third-octave bands helps optimize measures precisely (e.g., fan noise vs. fracture noise).
Building acoustics in rock excavation and tunnel construction
In rock and tunnels, the structure itself acts as a waveguide. Low-frequency waves travel far and can reach neighbors or existing structures. Hydraulic splitting using rock splitters and the targeted use of jaw or cutting techniques enable controlled separations with low impulses. Shielding is particularly effective in tunnels when mass and absorption are combined. Power pack locations, air routing, and transport chains (conveyor belts, cars) must be planned acoustically so that no elongated resonances arise.
Strip-out and cutting in existing structures
Interior spaces with hard, smooth surfaces have short distances and strong reflections. As a result, noise is perceived as more present. Acoustically favorable are steady methods with low impact excitation—such as crushing with concrete pulverizers or hydraulic splitting. When cutting metal (e.g., tank cutters, steel shears), resonances can be reduced by interlayers, clamping, and damped supports. For strip-out, small-scale dismantling, controlled placement, and soft interlayers significantly reduce peak levels.
Natural stone extraction and special operations
In natural stone extraction the acoustic environment is often open, yet sound can carry far in valleys. Rock and concrete splitters enable quiet separation with a low airborne sound share. In special operations—such as in sensitive facilities—reproducible cycles, demand-driven control of hydraulic power packs, and minimizing free fall heights have high acoustic effectiveness.
Typical measures to reduce emissions on site
The most effective levers lie in the combination of method selection, damping, and process control. The following measures have proven themselves in practice, especially in conjunction with Darda GmbH’s hydraulic tools:
- Instead of impact work: use concrete pulverizers or rock and concrete splitters wherever static separating methods are feasible.
- Close load paths: steer cracks via pre-drilling to avoid uncontrolled spalling.
- Smooth the cycles: constant feed and pressure ramps to minimize impulse peaks.
- Decouple power packs: elastic bearings, mass–spring concepts, low-turbulence cooling.
- Combine shielding: mass (barrier) plus absorption (internal damping) along direct line-of-sight paths.
- Dampen material handling: rubberized pads, quiet rigging, short free-fall heights.
- Use monitoring: acoustic feedback to continuously optimize settings and pacing.
Normative framework and organizational aspects
In planning and execution, recognized rules of technology and relevant standards and guidelines for noise control and vibrations are helpful. These set the framework for rating levels, measurement procedures, and thresholds of acceptability. Organizationally, early coordination with stakeholders, transparent communication of work phases, and documentation of measures taken are advisable. Legal requirements must be reviewed project-specifically; binding evaluations cannot be provided here.
Tool selection from an acoustic perspective
The choice between jaws, splitters, shears, or cutters depends on the component, material bond, and boundary conditions. From an acoustic perspective:
- Concrete pulverizers: quiet, low-impulse, well controllable in existing structures; suitable for concrete demolition and special demolition.
- Rock and concrete splitters: very low vibration and airborne sound shares; advantageous for sensitive uses, strip-out, and tunnel construction.
- Combination shears and multi cutters: cut/crush with moderate levels; uniform actuation is important.
- Steel shears and tank cutters: pay attention to clamping, support, and resonance avoidance; steady cutting action.
- Hydraulic power packs: a source of relevant airborne sound; location, decoupling, and fan concepts are decisive.
Occupational safety and health
Regardless of immission targets, protective measures for workers must be observed. Personal protective equipment, break and rotation schemes, and minimizing impulse-intensive work steps contribute to health protection. For planning and execution, the applicable legal requirements and recognized rules of technology are authoritative; project-specific specifications are set by those responsible on site.