Sound or noise

Sound is changes in air pressure that our ear can perceive. These vibrations propagate as waves through the air, where the waves consist of compressions and rarefactions of air molecules. All sound that reaches our ears is fundamentally the same physical phenomenon – pressure changes that our hearing organ converts into electrical signals that the brain interprets.

Noise is commonly defined as ”unwanted sound” – but this definition is complex because it is based on subjective experiences. A sound that is desirable in one context may be disturbing in another. Music can be enjoyable when you have chosen to listen to it, but experienced as noise when it penetrates through the wall from a neighbor. The subjective experience is influenced by factors such as:

• Sound volume and frequency content
• Time and place
• The activity we are engaged in
• Our attitude toward the sound source
• The ability to control the sound
• The information content of the sound
• Our individual sensitivity

Classifying a sound as noise therefore isn’t just about its physical properties, but also about how it affects us in a specific context. A faint but high-frequency beep from electronics can be perceived as more disturbing than a stronger but steady background noise. Natural sounds like waves or wind are often experienced as less disturbing than mechanical sounds of the same strength.

This complexity makes it challenging to set limit values for noise. While sound levels can be measured objectively in decibels, the assessment of what constitutes disturbing noise must take into account both the character of the sound and the context in which it occurs. This is particularly relevant for new sound sources in the environment, where there is limited long-term experience of how the sound affects people over time.