SEALED PIPE-LOADED LOUDSPEAKER FOR IMPROVING LOW FREQUENCY RESPONSE IN PORTABLE DEVICES

• US 20170318383A1
• Filed: 05/02/2017
• Published: 11/02/2017
• Est. Priority Date: 05/02/2016
• Status: Active Grant

• Current Assignee: Dolby International AB (Dolby Laboratories Incorporated)
• Original Assignee: Dolby International AB (Dolby Laboratories Incorporated)
• Inventors: GRIFFITHS, Kelvin Francis, DI CARLANTONIO, Giuseppe
• Granted Patent: US 10,536,769 B2
• Time in Patent Office: Days
• CPC Class Codes: H04M 1/03 Constructional features of telephone transmitters or receivers, e.g. telephone hand-sets
• CPC Class Codes: H04M 1/035 Improving the acoustic characteristics by means of constructional features of the housing, e.g. ribs, walls, resonating chambers or cavities
• CPC Class Codes: H04R 1/225 for telephonic receivers
• CPC Class Codes: H04R 1/2857 for loudspeaker transducers
• CPC Class Codes: H04R 2499/11 Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's

Abstract

Embodiments are directed to a sealed pipe-loaded loudspeaker for augmenting low frequency response in a portable electronic device. A loudspeaker transducer is configured to radiate sound directly out of a forward radiation area and incidentally out of a rearward radiation area, and a sealed transmission line forming a closed pipe acoustically coupled to the transducer through which the rearward radiation propagates to produce standing waves corresponding to the dimensions of the closed pipe, wherein resonances apply a loading to a diaphragm element of the transducer to lower its resonance frequency. An acoustical wave front radiates away from the diaphragm element for the direct sound and is emitted outside of the device, and the rearward radiation is not emitted from the device.

Claims

1. An apparatus comprising:

an audio transducer;

a transmission line acoustically coupled to the transducer configured to transmit sound waves generated by the transducer out of an area for forward radiation of sound;

a lid configured to acoustically seal the audio transducer and the transmission line; and

a digital signal processor functionally coupled to the transducer and configured to compensate for localized attenuation due to resonance within the transmission line.

2. The apparatus of claim 1 wherein the transducer is a miniature speaker on the order of up to 40 mm long on one side.

3. The apparatus of claim 2 wherein the transducer is mounted within a portable audio device selected from one of:

a mobile phone, a tablet computer, a notebook computer, and a portable game device.

4. The apparatus of claim 1 wherein the transmission line comprises a folded length within a cavity, and wherein the transmission line is one of a constant diameter line and a tapered line.

5. The apparatus of claim 4 wherein the length and the diameter of the transmission line are configured to generate pipe resonances that augment the very low frequencies of the audio signal.

6. The apparatus of claim 5 wherein the frequency range of the very low frequencies comprises 100 Hz to 500 Hz.

7. The apparatus of claim 6 wherein the transmission line comprises a set of partial baffles that create the folded length.

8. The apparatus of claim 1 wherein the digital signal processor executes an equalization and compression function to smooth any localized and peaky attenuation within a frequency response of the audio signal.

9. The apparatus of claim 3 wherein the transmission line is disposed within a frame portion of the portable audio device.

10. The apparatus of claim 9 wherein the transmission line is disposed within the frame portion in a space that is originally dedicated to the audio transducer.

12. The device of claim 1 further comprising a lid configured to acoustically seal the audio transducer and the transmission line, and wherein the transmission line is disposed within a space of the device dedicated to the audio transducer.

11. A portable electronic device comprising:

a body portion at least partially covering a frame defining an outline of the device;

an audio playback circuit comprising an amplifier and signal processing component;

an audio transducer disposed within a portion of the frame; and

a sealed transmission line acoustically coupled to the transducer configured to transmit sound waves generated by the transducer out of a sound radiation area, wherein the signal processing component is configured to compensate for localized attenuation due to resonance within the transmission line.

13. The device of claim 11 wherein the transmission line comprises a folded length within a cavity, and wherein the transmission line is one of a constant diameter line and a tapered line.

14. The device of claim 13 wherein the length and the diameter of the transmission line are configured to generate pipe resonances that augment the very low frequencies of the audio signal.

15. The device of claim 14 wherein the frequency range of the very low frequencies comprises 100 Hz to 500 Hz.

16. The device of claim 15 wherein the transmission line comprises a set of partial baffles that create the folded length.

17. The device of claim 11 wherein the digital signal processing component executes an equalization and compression function to smooth any localized and peaky attenuation within a frequency response of the audio signal.

18. The device of claim 11 wherein the portable device is selected from the group consisting of:

a laptop computer, a notebook computer, a tablet computer, a mobile phone, and a handheld game device.

19. A device comprising:

a loudspeaker transducer configured to radiate sound directly out of a forward radiation area and incidentally out of a rearward radiation area; and

a sealed transmission line forming a closed pipe acoustically coupled to the transducer through which the rearward radiation propagates to produce standing waves corresponding to the dimensions of the closed pipe, wherein resonances apply a loading to a diaphragm element of the transducer to lower its resonance frequency.

20. The device of claim 19 wherein an acoustical wave front radiates away from the diaphragm element for the direct sound and is emitted outside of the device, and wherein the rearward radiation is not emitted from the device.

21. The device of claim 19 wherein the transmission line comprises a folded length within a cavity of the device, and is sealed by a lid to form the closed pipe.

22. The device of claim 21 wherein the length and the diameter of the transmission line are configured to generate pipe resonances that augment the very low frequencies of the audio signal.

23. The device of claim 22 wherein the frequency range of the very low frequencies comprises 100 Hz to 500 Hz.