Earplug and method for attenuating sound

1. An earplug for attenuating sound from an outside surroundings to an ear canal, the earplug comprising:

a housing comprising an ear tip configured to form an acoustic seal with the ear canal; and

an acoustic canal extending straight through the housing to guide the sound from the outside surroundings to inside the ear canal, the acoustic canal comprising:

a canal section having a first diameter that is dimensioned to fit at least partially inside the ear canal, the canal section ending at one side in a first exterior opening that is in use directed to let the sound into the ear canal, wherein another side of the canal section transitions into

a first resonance volume starting from an end of the canal section with a second diameter that is wider than the first diameter; the acoustic canal further comprising

a second resonance volume with a third diameter that is wider than the second diameter and ending at one side in a second exterior opening that is in use directed to the outside surroundings for receiving the sound, wherein another side of the second resonance volume is separated from the first resonance volume by a sound attenuating mesh bounding one side of each of the resonance volumes;

wherein the acoustic canal is directed along a straight line between the second exterior opening and the first exterior opening which is oppositely facing said second exterior opening;

wherein a combined length of the canal section and the first resonance volume, measured between the sound attenuating mesh and an edge of the first exterior opening is between one and two centimeters;

wherein a volume of the first resonance volume is larger than a volume of the canal section;

wherein the first and second resonance volumes form at least part of respective first and second resonance cavities separated by the sound attenuating mesh;

wherein the canal section and the first resonance volume are configured to form, in combination, the first resonance cavity with a first resonance peak for the sound in a first frequency range between two and five kilohertz;

wherein the second resonance volume is configured to form the second resonance cavity with a second resonance peak for the sound in a second frequency range between five and ten kilohertz;

wherein the first and second resonance cavities are configured to provide the first and second resonance peaks that partially compensate attenuation of the sound attenuating mesh in a resonance frequencies range above one kilohertz.

2. The earplug according to claim 1 , wherein the earplug comprises two parts that fit together with a controllable distance defining a variable volume of the first resonance cavity.

3. The earplug according to claim 1 , wherein the acoustic canal is configured to provide at least the first and second resonance peaks that partially counteract attenuation of the sound by the sound attenuating mesh in respective frequency ranges around the at least the first and second resonance peaks.

4. The earplug according to claim 1 , wherein maxima of the resonance peaks are at least two kilohertz apart.

5. The earplug according to claim 1 , wherein the combined length of the canal section and first resonance volume, measured between the sound attenuating mesh and the edge of the first exterior opening is less than seventeen millimeter.

6. The earplug according to claim 1 , wherein the second diameter is larger than the first diameter by a factor one-and-half or more.

7. The earplug according to claim 1 , wherein the volume of the first resonance volume is larger than the volume of the canal section, by a factor one-and-half, or more.

8. The earplug according to claim 1 , wherein a normal of the sound attenuating mesh is tilted at an angle with respect to a centerline of the acoustic canal for increasing its effective surface.

9. The earplug according to claim 1 , wherein the second resonance volume is formed by a surrounding mantle section ending at one side with the sound attenuating mesh and at the opposite side in the second exterior opening to the outside surroundings, wherein the mantle section comprises one or more additional side openings to improve directional hearing.

10. The earplug according to claim 1 , wherein the canal section is formed by a relatively narrow first tubular part covered by a flexible exterior configured to adapt its form to an entry of the ear canal, wherein the first resonance volume and second resonance volume are formed in a relatively wide second tubular part, wherein the second tubular part comprises the sound attenuating mesh separating the first resonance volume and second resonance volume, wherein the first and second tubular parts fit together to form the earplug.

11. A method for attenuating sound from an outside surroundings to an ear canal, the method comprising:

providing a housing comprising an ear tip to form an acoustic seal with the ear canal; and

providing an acoustic canal extending straight through the housing to guide the sound from the outside surroundings to inside the ear canal, the acoustic canal comprising:

a canal section having a first diameter that fits at least partially inside the ear canal, the canal section ending at one side in a first exterior opening that lets the sound into the ear canal, wherein another side of the canal section transitions into

a first resonance volume starting from an end of the canal section with a second diameter that is wider than the first diameter; the acoustic canal further comprising

a second resonance volume with a third diameter that is wider than the second diameter and ending at one side in a second exterior opening that receives the sound, wherein another side of the second resonance volume is separated from the first resonance volume by

a sound attenuating mesh bounding one side of each of the resonance volumes;

wherein the acoustic canal is directed along a straight line between the second exterior opening and the first exterior opening which is oppositely facing said second exterior opening;

wherein a combined length of the canal section and the first resonance volume, measured between the sound attenuating mesh and an edge of the first exterior opening is between one and two centimeters;

wherein a volume of the first resonance volume is larger than a volume of the canal section;

wherein the first and second resonance volumes form at least part of respective first and second resonance cavities separated by the sound attenuating mesh;

wherein the canal section and the first resonance volume are configured to form, in combination, the first resonance cavity with a first resonance peak for the sound in a first frequency range between two and five kilohertz;

wherein the second resonance volume is configured to form the second resonance cavity with a second resonance peak for the sound in a second frequency range between five and ten kilohertz;

wherein the first and second resonance cavities provide the first and second resonance peaks that partially compensate attenuation of the sound attenuating mesh in a resonance frequencies range above one kilohertz.

12. The method according to claim 11 , further comprising providing a normal of the sound attenuating mesh tilted at an angle with respect to a centerline of the acoustic canal for increasing its effective surface.