Interference noise-control unit

A process for making an interference noise-control unit, comprising the steps of:

• forming a case,
• injection moulding an insert wherein said case and said insert form a housing,
• mounting said case on a sound arresting wall, and
• mounting said insert to said case, wherein the housing comprises a hollow compartment comprising at least one first channel and at least one second channel, wherein
• said first channel has a first channel height A and a first channel length B, and wherein
• said second channel has a second channel height A′ and a second channel length B′, and wherein said first channel height A is different from said second channel height A′,
• a third channel having a third channel height A″ which is equal to or smaller than said second channel height A′ and a third channel length B″ which is equal to or smaller than said second channel length B wherein a relationship between a second channel height A′ to a third channel height A″, is in an interval of 1.1-3.0 and wherein said insert comprises a plurality of baffles forming said first, second and third channels.

An interference noise-control unit, for installation on a sound arresting wall for reducing noise from trains, comprising:

• a housing to be secured on a sound arresting wall, wherein the housing comprises a hollow compartment comprising at least one first channel and at least one second channel, wherein
• said first channel has a first channel height A and a first channel length B, and wherein
• said second channel has a second channel height A′ and a second channel length B′, and wherein said first channel height A is different from said second channel height A′,
• wherein a relationship between said first channel height A and said second channel height A′ is in an interval of 1.1-3.0, and
• wherein said housing comprises a case and an insert, said insert comprising a plurality of baffles forming said channels.