Acoustics

Question 1

What are the learning objectives?

Answer 1

• Describe planning, construction, and operation of buildings and technical systems.
• Understand relevant regulations, norms, and laws in urban planning and environmental work.
• Perform basic assessments of how traffic noise and vibrations affect health and urban planning.

Question 2

What is the difference between sound and noise?

Answer 2

Sound = vibrations in air or materials.
Noise = unwanted and/or harmful sound.

Question 3

How is sound measured?

Answer 3

Measured in decibels (dB), logarithmic scale.

Question 4

What are typical urban sound levels in dB?

Answer 4

• Whisper: ~30 dB
• Normal conversation: ~60 dB
• Truck starting: ~90 dB
• Jet engine nearby: ~120–140 dB
• Pain threshold (smärtgräns): ~130 dB

Question 5

What are common noise sources in cities?

Answer 5

• Traffic: road, rail, air, boats
• Industry and construction
• Ventilation, fans
• “Life sounds”: children, birds, water, rustling leaves

Question 6

What are health effects of traffic noise?

Answer 6

• Irritation
• Cardiovascular disease
• Sleep disturbances
• Reduced cognitive function
• Mental health impact (less studied)

Question 7

What are the WHO guidelines on noise exposure?

Answer 7

• Relationship between sound level (Lden) and annoyance/sleep disturbance.
• WHO emphasizes importance of long-term exposure.
• New sources included: wind turbines, recreational noise.

Question 8

What are sources of ground vibrations?

Answer 8

• Sources: trains, trams, heavy vehicles, piling, etc.
• Effects: vibrations in buildings, structural-borne sound (stomljud) (audible inside).

Question 9

What are mitigation (åtgärder) strategies for ground vibrations?

Answer 9

• Rail isolation from ground
• Physical barriers (sheet piles, trenches)
• Property buyouts in extreme cases

Question 10

What does modern urban planning focus on?

Answer 10

• Dense, mixed-use neighborhoods
• Shorter distances
• Traffic integration

Question 11

How can building design protect against noise?

Answer 11

• Enclosed blocks (slutna kvarter) → quiet courtyards
• Bedrooms facing courtyards
• Glazed balconies
• Sound-absorbing roofs and facades (e.g., green walls)
• Irregular facades reduce sound reflection

Question 12

What are traffic strategies for noise reduction?

Answer 12

• Spatial concentration: concentrate traffic on key streets → quieter housing overall
• Traffic calming: speed reduction, smoother driving
• Quiet asphalt (porous): common in Europe, rare in Sweden due to studded tires

Question 13

What are examples of noise reduction in urban areas?

Answer 13

• Bomgatan: 53 → 43 dB
• Partille: 64 → 54 dB
• Övre Husargatan: street design → lower noise

Question 14

What is the significance of quiet sides and recreation?

Answer 14

• Quiet side = e.g., courtyard with <50 dB → supports recovery
• Access to green areas with natural sounds is important
• Recreational value drops sharply above 50 dB

Question 15

What are the Swedish noise guidelines?

Answer 15

• Indoors (day/night): max levels depending on time
• Facade levels: limits vary by zone
• Outdoor areas (patios, balconies): specific limits
• Exceptions allowed – less strict than air quality rules

Question 16

What are urban planning best practices for noise reduction?

Answer 16

• Bedrooms facing the courtyard
• Avoid ground-floor housing near noisy streets
• Small, enclosed blocks
• Reroute (väg bort) noisy vehicles at night
• Provide nearby green areas
• Use noise-dampening materials and landscaping
• Avoid using noise barriers where possible (can degrade street quality)