Airborne sound accompanies almost every intervention in concrete, rock, and steel. Whether in concrete demolition, the gutting of a structure, tunnel construction, or natural stone extraction—pressure fluctuations arise in the air everywhere and are perceived as noise. For working with product groups from Darda GmbH—such as concrete demolition shears, stone and concrete splitters, hydraulic power packs, combination shears, Multi Cutters, steel shears, or tank cutters—a solid understanding of airborne sound is essential in order to align planning, operation, and protective measures professionally.
Definition: What is meant by airborne sound
Airborne sound consists of sound waves that propagate as changes in air pressure. Causes include mechanical processes such as cutting, pressing, splitting, or striking. The sound pressure level is typically given in dB(A) and describes the strength of the perceived noise. Character and impact depend on the frequency spectrum (low, mid, high), temporal structure (continuous noise, impulsive noise), and propagation (distance, reflections, shielding). Airborne sound is distinct from structure-borne sound, which propagates in solid materials and can secondarily radiate airborne sound from surfaces.
Physical fundamentals and generation of airborne sound
Airborne sound arises when components, tools, or machines set the surrounding air into oscillation periodically or impulsively. In pressing and cutting (e.g., with concrete demolition shears or combination shears), spectra are often broadband but less impulsive. In splitting (e.g., with stone and concrete splitters or rock splitting cylinders), characteristic cracking sounds occur, with peak levels that may rise briefly. Striking methods, by contrast, typically generate pronounced impulses and higher peak levels. Hydraulic power packs contribute valve, pump, and fan noise to the continuous level. Propagation approximately follows the distance law: with each doubling of distance, the level in free field typically decreases by about 6 dB; in practice, reflections, ground characteristics, and wind influence the resulting immission level.
Sources of airborne sound on the construction site and in the quarry
Depending on the work method and construction site layout, the type and level of noise emissions differ. Typical sources include:
- Tools for concrete and steel processing: Concrete demolition shears, combination shears, Multi Cutters, steel shears, and tank cutters generate noise through cutting, pressing, and separating processes on concrete, rebar, and steel components.
- Stone and concrete splitters: Stress build-up in the material and subsequent crack growth lead to short, sometimes abrupt airborne sound events.
- Hydraulic power packs: Pumps, valves, and fans cause broadband continuous noise; housings, lines, and attachments can additionally radiate.
- Peripheral equipment: Transport, feeding, hoists, and material handling generate tonal or impulse-like components.
- Environment-related background noise: Reverberation in interior spaces, tunnel and shaft reflections, facade reflections, meteorological influences.
Airborne sound in the context of concrete demolition shears and stone and concrete splitters
The choice of method decisively shapes the noise profile. Concrete demolition shears work by cutting and pressing; they generally produce less pronounced impulse peaks than strongly percussive methods. Airborne sound arises primarily from breaking the concrete structure, severing the rebar, and radiation at free edges. Stone and concrete splitters—including rock splitting cylinders—transfer energy into the material via controlled pressure build-up. The acoustic result is short cracking events whose frequency and level depend on geometry, material quality, prestress, and execution of the splitting process. In noise-sensitive environments, a targeted combination of shearing and splitting processes can reduce overall levels, for example by minimizing percussive components and by thoughtful sequence planning.
Emission, propagation, and immission of airborne sound
Three levels are relevant for planning: emission at the tool or power pack, propagation over the site, and immission at workplaces and sensitive receivers. Key aspects include:
- Distance and geometry: Doubling the distance significantly reduces the level outdoors. Edges, courtyards, and interiors amplify via reflections. Tunnels and shafts guide and channel sound.
- Frequency dependence: Higher frequencies are more strongly attenuated by air and obstacles; low-frequency components carry farther and are harder to shield.
- Shielding: Massive, dense barriers close to the source reduce line-of-sight and direct sound. Gaps, openings, and leaks diminish the effect.
- Ground and vegetation: Soft ground and vegetation absorb part of the sound; hard surfaces reflect.
- Meteorology: Wind direction and temperature gradients can refract sound upward or focus it near the ground.
Measurement and evaluation of airborne sound
Assessment is performed with sound level meters using A-weighting and suitable measurement periods (e.g., equivalent continuous sound level). In practice, one distinguishes workplace measurements (near the source) and immission measurements (e.g., at property boundaries). Relevant, in addition to Leq, are maximum levels and impulsive events. For comparability, measurement points, time windows, and operating conditions should be clearly documented. Normative details and limits are project-specific and depend on applicable regulations; they must be carefully reviewed in each individual case.
Noise-reducing measures in practice
Planning and sequencing
- Schedule work phases with elevated airborne sound in favorable time windows; temporally decouple sensitive tasks.
- Position noise-intensive power packs as far as possible from sensitive areas; minimize paths and lines of sight.
- Plan construction logistics to avoid material handling and idle operations with high levels.
Method and tool selection
Cutting and pressing methods—such as with concrete demolition shears, combination shears, Multi Cutters, and steel shears—tend to generate less impulsive noise than strongly percussive methods. Stone and concrete splitters as well as rock splitting cylinders operate in a controlled manner; the short cracking events can be influenced by suitable clamping technique, step increments, and material preparation. Tank cutters should be operated with a stable support, constant feed, and decoupled workpieces to reduce vibrational excitation and secondary noise.
Maintenance, hydraulics, and peripherals
- Check hydraulic power packs: operate pumps, valves, and fans with low noise (e.g., appropriate to speed and temperature), seal housing joints, ensure vibration decoupling.
- Keep tools sharp and free of play; dull cutting edges increase excitation, prolong processes, and raise airborne sound.
- Secure hoses and lines, avoid hard contacts, damp attachments.
Site setup and shielding
- Place mobile noise barriers or containers as acoustic barriers close to the source.
- Position material stacks, earth berms, and machines strategically to interrupt direct sound paths.
- Indoors: close openings; subdivide reverberant surfaces using fore-placed elements or absorbing building materials.
Communication and documentation
Transparent information for affected parties, clear operating hours, and traceable measurement and record-keeping support acceptance. Legal requirements are project-specific and must be reviewed; binding statements can only be made within the scope of the relevant standards and permits.
Special application areas: targeted control of airborne sound
Concrete demolition and special deconstruction
During the deconstruction of massive structural elements, airborne sound components arise from separation, crushing, and fracture processes. Alternating between concrete demolition shears for selective separation and targeted splitting for volume-reducing measures can reduce impulse components and limit sound duration. Short free paths between the source and outside air, as well as using existing structural elements as shielding, are important.
Building gutting and cutting
During gutting, reverberation and decay times in rooms are particularly pronounced. Cutting methods with combination shears, Multi Cutters, or steel shears benefit from decoupled support of the workpieces and segmented procedures to smooth airborne sound peaks. For tank cutters, the following applies: stable seating, controlled feed, and avoidance of resonances through defined clamping points.
Rock excavation and tunnel construction
In tunnel bores, airborne sound is channeled; reflections increase levels in certain zones. Stone and concrete splitters as well as rock splitting cylinders act directly in the rock; the elastic energy released manifests as a short cracking sound. Coordinated pacing, acoustic shielding behind the working face, and routing power packs into side adits reduce immission.
Natural stone extraction
In quarries, topography determines propagation: free-field conditions favor distance attenuation, rock faces reflect. Controlled splitting enables large-block extraction with manageable airborne sound. Hydraulic power packs should be operated in depressions, behind berms, or barriers to interrupt direct sound.
Special operations
In sensitive environments—such as near protected facilities—a combination of low-noise methods, tight time planning, and consistent shielding is effective. Short, plannable noise events are often easier to control than long-lasting continuous levels.
Health and occupational safety when dealing with airborne sound
At workplaces with elevated airborne sound, suitable protective measures must be provided. These include personal protective equipment (e.g., hearing protection), break arrangements, and minimizing exposure through task rotation and distance. The specific design is based on applicable regulations, operating instructions, and risk assessments for the respective project.
Practical guide: step by step to a quieter construction site
- Identify sound sources: tools, power packs, and handling processes; prioritize them.
- Process analysis: evaluate cutting, pressing, and splitting with respect to impulse and continuous components.
- Optimize layout: increase distances, place barriers near sources, break lines of sight.
- Align tool selection: where possible, combine cutting/pressing methods (e.g., concrete demolition shears) sensibly with splitting processes.
- Dampen power packs: encapsulate hydraulic power packs, optimize fan guidance, decouple vibrations.
- Cadence operations: cluster noise peaks, avoid sensitive times, synchronize workflows.
- Ensure maintenance: keep cutting edges sharp, avoid leaks, check fastenings.
- Verify effectiveness: document measurements, fine-tune measures.
Typical misconceptions about airborne sound
- “Only the dB value matters.” — Time structure, frequency content, and impulse peaks also significantly shape perception.
- “Just placing barriers somewhere is enough.” — Effectiveness primarily arises from short source-to-barrier distance and closed shielding.
- “Hydraulic power packs are secondary.” — Continuous levels from power packs often shape overall exposure more than brief tool operations.
- “Low frequencies are harmless.” — Low-frequency sound carries far and is harder to attenuate; planning and positioning are critical.