Inspection methods and standards for earphones

Views: 76     Author: Site Editor     Publish Time: 2022-11-25      Origin: Site

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A headset is a pair of conversion units that take signals from a media player or receiver and convert them into audible sound waves using speakers close to the ear. From the development of the audio industry as a whole, wireless headphones are still a new thing, the development time is not long, is still in the rising period, user demand continues to improve, the user's expectations of wireless headphones are also improving, which is a new test for the industry. With the increase of users, users have higher and higher requirements for the quality of earphones, which makes the inspection and detection of earphones more important. So how do you check headphones? This article will give you a detailed introduction to the inspection methods and standards of headphones.

1. Basic knowledge of headphones

1. Classification of earphones

Although there are a variety of headphones on the market, the variety of headphones is essentially limited.

According to the product structure can be divided into: open, semi-open and closed;

From the way of wearing can be divided into: head wear type, earplug type, in-ear type, after hanging type, ear hanging type;

According to the principle of energy exchange is divided into: moving coil type and electrostatic type

The composition of the headset:

Headbands: Headbands are generally divided into steel headbands and plastic headbands. Steel head belt is generally in a PVC hose with a steel beam, there are also double head belt with a single head belt. The headphone with steel headband structure is usually equipped with an elastic leather headband outside the steel beam to adjust the comfort of wearing. The plastic headband is generally made of PP material. The plastic of this material is soft and resilient.

Lock piece: plastic/steel strip (metal); Headband headphones are for that

Support: plastic/steel strip (metal); Headband headphones are for that

Ear shell: The material of ear shell is usually plastic, metal and wood. The surface spray paint is generally divided into ordinary paint, UV paint and rubber paint.

UV paint is a transparent and bright UV oil sprayed on the ordinary paint, so that the surface texture of the product is more smooth and bright. Rubber paint is a kind of rubber oil sprayed on the ordinary paint to make the surface of the product feel more soft.

Earmuffs: Earmuffs are generally made of sponge, flannelette, leather and silica gel.

Sponge earmuffs are breathable, inexpensive, but easily damaged; Flannelette earmuffs are comfortable to wear, but easy to dirty; Leather ear muffs have good texture, giving people a feeling of more upscale, but not breathable, not suitable for summer wear; Silicone earmuffs are cool to wear and ideal for summer use.

Horn: NdFeb material, caliber: general f9, f10, f30, f40, f50.

External microphone/wire: plastic microphone rod (gooseneck tube), microphone head (plastic);

A small accessory on an earpiece that acts as a decoration;

Wire: Length: Walkman about 1.2 meters, home computer about 2.2 meters; Material: Insert the general leather wire and braided wire (wiring) two. Leather thread good texture, soft, elastic; Braided thread is more resistant to wear and stretch, but less elastic.

The cable of a wheatless headset is usually three cores: ground cable, left and right signal cable; There are usually two specifications of 4-core and 5-core cable for headphones with microphone. The 4-core cable is shared by the left and right bottom lines, and the effect is not as good as the 5-core cable. The general brand of earphone wire will have anti-breaking wire, if there is no anti-breaking wire, the earphone will be scrapped in less than 1 month. This kind of earphone will not have in foreign countries, you understand. Most headphone cables are made of copper, and the general purity (usually expressed by a few N, such as 4N, 6N......) The higher the electrical conductivity is, the better the signal distortion is. The common ones are: TPC (electrolytic copper) : purity of 99.5% OFC (oxygen free copper) : purity of 99.995% LC-OFC (linear crystal oxygen free copper or crystal oxygen free copper) : purity of 99.995% or more OCC (single crystal oxygen free copper) : High purity, more than 99.996%, and is divided into PC-OCC and UP-OCC.

Plug: The headphone plug is divided into 6.35mm and 3.5mm, 2.5mm, USB four kinds. The surface of the plug is divided into two kinds: gold plating and nickel plating, gold plating has better oxidation resistance. We see more 3.5mm, USB head is used on the computer, are come with the sound card.

Wire control: adjust the volume, there is a tuning button;

Mouse tail: a leather ring (guard coil) connecting the middle of two components;

A solid rubber covering between one line and two lines;

2. Important parameters of the headset

(1) Impedance common standard: 16/32 ohm ±3-15% (depending on guest requirements)

Earphones with small impedance are easy to be driven by audio equipment. Because CD and MP3 themselves have little power, it is suitable to choose low-impedance earphones, usually below 32 ohms.

(2) Sensitivity common standard: 90-120db

For portable players such as MP3 players, higher sensitivity means more music details can be heard at the same volume. A wide range of headphones, sensitivity is better than 100d;

(3) Common frequency response range standard: 20-20KHz

The normal ear can hear sound within a frequency response range of 20-20 KHZ, so the closer the frequency response range is to this range, the more complete the sound will be. Reflected in the listening effect, is the more detailed.

Ii. General inspection specifications for earphones

(1) Inspection tools

Ruler, vernier caliper, plug gauge, comparison piece, bar code gun, ESD gloves or finger covers, dust cloth, alcohol, knife, box sealing tape, and Scotch tape.

(2) Inspection conditions

Visual acuity: the visual acuity of the inspector shall be no less than 1.0(including corrected visual acuity);

Distance: the distance between the human eye and the tested mobile phone surface is 300mm±50mm; Lighting: cold white fluorescent lamp (the light source is directly above the tester), illuminance is 1000±200Lux;

Temperature: 15-35℃;

Humidity: 20%-75%;

View Angle: The product view surface should be at a 45 degree Angle from the desktop, and rotate 45 degrees up and down (as shown below) :

(3) Definition of defects

1. Definition of assembly defects of the whole machine

Segment difference: The theoretical design of the assembly surface of two parts is zero deviation. Due to the machining error, the dislocation deviation of the actual assembly surface is generated.

Surplus: In normal use, face the use of the surface to see the segment difference.

Deficit: In normal use, face the use of the surface can not see the segment difference.

2 Definition of defective plastic parts

Point defect: A defect having a point shape, the larger diameter of which shall be used in measurement.

Heterochromatic point: A point on the surface of a plastic that is different in color from the surrounding point.

Bubble: Because the raw material is not sufficiently dry, resulting in the formation of the product inside the shrinkage hole.

Multiple glue points: small plastic bumps on the surface of the product caused by mold damage.

Shrinkage: When the plastic melt passes through a thin section, its pressure loss is large, it is difficult to maintain high pressure to fill the hole formed in the thick section.

Glitter: For non-smooth plastic parts, due to uneven wall thickness, the local shiny phenomenon at the wall thickness change. Hard scratch: Deep scratch on the surface of plastic parts caused by friction with hard objects.

Fine scratch: A scratch without depth on the surface of a plastic piece.

Flying edge: Plastic waste edge on the edge or parting surface of a plastic part due to injection molding parameters or mold.

Fusion wiring: When plastic melt flows in the cavity, it encounters obstacles (core and other objects). After bypassing the obstacles, the melt cannot fuse well, so an obvious line is formed on the surface of the plastic part, which is called fusion wiring.

Warping: Plane deformation of plastic due to internal stress.

Top white/top bump: Due to the large wrapping force of the plastic parts, the top bar area by the strong top force produced by the white mark or bump.

Insufficient filling: Due to insufficient injection pressure or poor exhaust in the mold cavity, the melting resin can not reach a certain corner of the mold cavity and caused by insufficient injection material.

Silver stripe: A silvery white stripe on a plastic surface along the direction of resin flow.

Rhymes: tree-ring streaks on the surface of a product centered around the gate.

Scorch: Localized blackening of plastic that appears on the surface of plastic parts.

Edge drag: due to the injection pressure is too large or the cavity is not smooth, the edge of the release caused by the abrasion.

Cracking: Cracks or small cracks caused by internal stress or mechanical damage.

Chromatic aberration: The color difference between the product surface and the standard sample is called chromatic aberration.

Impurities: There are foreign bodies mixed with raw materials for medium reasons, forming on the surface of the product shows spots.

Rainbow phenomenon: refers to the transparent area under the condition of reflective color halo phenomenon.

Deformation: due to the uneven shrinkage of the molding product, resulting in the formation of stress inside the molding product.

Bite defects: Due to the length of discharge time, the strength of current or the improper control of corrosion time, the bite pattern or pattern on the surface of the plastic parts is different from the standard sample.

Poor transparency: refers to the phenomenon of fuzzy and poor transparency in the transparent area.

Light transmission: the printing area has a part of the printing, so that the light can be passed from the back to the front, known as light transmission.

3. Definition of defective painting parts

Point defect: A defect having a point shape, the larger diameter of which shall be used in measurement.

Particles: Fine particles attached to the surface of the spray paint.

Hard scratch: Deep scratch on the surface of the paint parts caused by the friction of hard objects.

Fine scratch: No deep scratch on the surface of the spray paint, it does not look obvious.

Paint accumulation: A local accumulation of paint on the surface of the painted parts.

Shadow: An area of paint or plastic that appears darker than the surrounding area.

Orange lines: large areas of fine orange peel shape on the surface of painted parts or electroplated parts.

Penetration: The phenomenon that the local paint layer is too thin on the surface of the painted parts and the matrix color is exposed.

Fisheye: As a result of the solvent volatilization rate caused by discomfort on the surface of the paint parts have a depression or small pit.

More spray: exceed the spray area specified on the drawing.

Spalling: The phenomenon of coating peeling off the surface of the product.

Catkins: Fibrous catkins carried within the paint itself or falling on the surface of the paint while the paint is not dry.

Chromatic aberration: The color difference between the product surface and the standard sample (customer recognized sample) is called chromatic aberration.

Poor gloss: The surface of the product is not consistent with the standard sample (customer admitted sample).

Fingerprint: A finger impression on a product surface or a shiny surface of a part.

Heterochromatic spot: A spot on the surface of a product with a color different from the surrounding spot.

Mist: The surface of the product has a poor gloss and looks like a mist.

Shrinkage: Shrinkage on the surface of plastic parts, but not covered or more obvious after painting.

Bubble: Because the raw material is not sufficiently dry, resulting in the formation of the product inside the shrinkage hole.

Multiple glue points: small plastic bumps on the surface of the product caused by mold damage.

Pitting: Dense granular spot defects.

Uneven color: Due to spraying parameters or process problems, the surface luster or color of the same product is inconsistent.

Poor light transmission: When the product shell is required to achieve light transmission effect, the surface light transmission effect is not the same as the expected light transmission

4. Definition of hardware defects

Leakage plating: No plating where plating should be.

Coating shedding: due to poor adhesion of coating caused by the separation between coating and substrate.

Rust spot: due to the lack of good plating, resulting in chemical reactions between the substrate and the external environment.

Pits: electroplating process is not well controlled resulting in small pits on the surface of electroplated parts.

Bruise: Surface damage caused by external force.

Burr: Excess scrap at the edges of parts.

Bubble: part surface of the local area of the coating bulge phenomenon.

Shrinkage hole: hole with irregular shape and rough surface caused by insufficient internal compensation during the condensation process of die casting.

Undercasting: The metal liquid is not filled with the cavity, and there is an incomplete filling part on the casting.

Rough: The coating surface is not smooth.

Fine scratch: A scratch with no depth.

Hard scratch: A deep scratch.

Uneven color: the luster and color of the surface of the parts show uneven phenomenon.

Warping/distortion: The surface of the part is uneven.

Grease: Grease attached to the surface of a part.

Indentation point: an indentation on a surface.

Poor gloss: The surface of the product is not consistent with the standard sample (customer admitted sample).

Pitting: Dense granular spot defects.

Chromatic aberration: The product surface shows a color difference from the standard sample (customer accepted sample).

Uneven color: Due to the anode parameters or mold design itself, the surface luster or color of the same product is inconsistent

5. Definition of defective printing/printing images

Printing position and alignment: deviation from specified printing position.

Printing style inconsistency: printing pattern and specification inconsistency during printing.

Color and tone differences: Color and tone deviations from specifications.

Thickness and flatness difference: thickness and flatness deviation from specification requirements.

Missing corner: image font defect.

Divergence: The edges of the text blur.

Thin line: The phenomenon that the width of a printed text or pattern line is reduced because it is not fully printed.

Mutilation: The appearance of a partial unprinted line of a printed text or pattern, including at the edge or center of an ink film.

Broken line: The phenomenon of interrupted printing lines and no ink stains (exposing the base).

Cracking: small cracks and roughness on the surface of printing ink film.

Net mark: The phenomenon of screen marks on the printing ink film due to poor ink fluidity.

Burr: The phenomenon of jagged ink film at the edge of the printing line due to ink penetration in the air.

Yin ink: refers to ink overflow on the outside of the printing line.

Orange peel: printing ink film surface is not smooth, orange peel like uneven phenomenon.

Overprint: that is, an overlapping film of ink, often seen in color printing.

Zink: A blotchy impression that appears in the graphic and dark parts of a print.

Flying ink: when the screen and the substrate is separated, the ink is not disconnected in time and is drawn into a filament, slowly pulled off and then fell to the two sides, thus forming a phenomenon of vertical filaments with imprinting.

Overprinting: when more than two colors are printed, each color separation layout text can achieve and maintain accurate alignment; The inaccuracy of overprinting is the error of imprinting overlap in the process of color printing -- the printing position is not correct, resulting in dislocation and blank phenomenon.

Wipe: The regional trace of a printed product caused by friction.

Ink bar: A distinct dark streak of dot expansion in a local area due to the instantaneous sliding friction of the ink roller in contact with the plate surface.

Water bar: due to the instantaneous sliding friction between the water roller and the plate surface, the dot narrowing in the local area produces an obvious light white stripe.

Deep scratch: The scratch has a certain depth, with the touch of the hand can feel its obvious concave on the surface of the printing. Slight scratch: The scratch on the surface of the print is not felt when touched by hand.

Pothole: The phenomenon that the surface cardboard and the pothole paper are not bonded properly.

Explosive knife burst line: the product forming along the beer cutting indentation split.

Burst/paint off: The phenomenon of ink shedding on the printed surface.

Brittle: The phenomenon that the surface cracks when bending the printed material.

Out-of-line/off-line: The adhesive position of the carton exceeds or does not reach the specified size.

Smudge: Printing ink printed on a substrate that sticks to the back of another sheet, causing a smudge.

Chromatic aberration: The color difference between the product surface and the standard sample is called chromatic aberration.

Bubbles: The phenomenon of small bubbles on the surface of the coated color box.

Crease: The phenomenon of creasing on the surface of the coated color box.

Stripe: A strip impression that appears on a printed surface.

Heterochromatic point: A point on the surface of a plastic that is different in color from the surrounding point.

Dirt: including hand prints, oil stains, fingerprints, stains, white fog and other undesirable phenomena.

Glue overflow: in the natural processing technology of color box, the adhesive part overflows the specified paste area due to too much glue.