Natural Melody Technology Inc.

Quality Assurance

Quality Organization

Total : 32 people | Engineer : 6 people | Inspector : 22 people | Acoustic : 4 people

Quality Control Process


Committee Team:RD, PE ,MFG, QA ,Purchasing
  • Objective
    To solve the raw materials, WIP and finished products in any quality issue influence production plan
  • Abnormal submission
    According to the abnormal material contact The FOrm or respectively production abnormal contact The FOrm
    Material --- IQC
    Process and WIP --- IPQC
    Finished goods --- OQC
  • Methods
    The FOrmulate short-term and long-term countermeasure
  • Exception handling results
    QA is responsible The FOr the validation of temporary and permanent countermeasure and tracking.

Supplier Management


Not in AVL list of new suppliers, put The FOrward by purchasing requirements according to apply process


Build up a team including QA, RD and Purchasing engineer to perThe FOrm on site audit and evaluate quality assurance system The FOr a score. Three times of Audit NG as never deal makers.


According to the results of the Audit score (at least 80% of 320 points) as a qualified supplier.
Kick off trial run The FOr production verification


IQC record all of inspection date and create production history report system to monitor quality status


Monthly statistics the situation of the quality score of current AVL suppliers, to suppliers in a low score and put The FOrward the planning orientation programs to improve within a time limit

Incoming Quality Control

Procedure : According to the incoming material control procedures "NM - 2 - Q - 006.
Vibrator : diaphragm, damper, voice coil, paper tube, dust cap
Holder: YOKE, magnets, washers, terminals, PCB, wire, plastic, ceramic chip.
Accessories: Tone paper, seals, EVA, nonwoven fabric, dust-proof net, rubber, packaging
According to the golden sample, WI and MIL - STD - 105E II single sampling plan
Appearance: AQL = 0.65 , Mechanical: AQL = 0.25
Function perThe FOrmance: 10 PCS, Dimension: 20 PCS/batch,
In accordance with the RE = 1, AC = 0 The FOr inspection determination
Quality Skill and Statistical report:
Histogram , Trend chart
2D Projector2D Projector
3D Projector3D Projector
Salt spray testerSalt spray tester

In Process Quality Control

First Article Inspection
When: production line start including ECN implement
Items: assemble/equipment/fixture/glue
WIP inspection
10 pcs sampling per 2 hours In accordance with the RE = 1, AC = 0 for inspection determination

Quality skill and statistical report:
Pareto, Cpk, Cause-Effect diagram, Trend chart
Process control point:
Equipment: glue machine, soldering, oven, frequency sweep, distortion, impedance, polarity
Frequency: dispensing machine one time per hours, others one time per 4 hours
The FO instrumentThe FO instrument
Frequency sweep meterFrequency sweep meter
Impedance instrumentImpedance instrument
gauss metergauss meter

Final Quality Control

Procedure: According to FQC inspection procedures NM - 2 - Q – 002
The FOllow the WI to do 100% inspection in production line


Quality skill and statistical report:
Pareto, Trend chart, Cause-Effect diagram
KlippelSound checkSunlight
The SPL curveThe SPL curveThe SPL curve
The distortion testThe distortion testThe distortion test
The impedanceThe impedanceThe impedance
The FOThe FOThe FO
The polarityThe polarityThe polarity
Rub   BuzzRub   BuzzRub   Buzz
FO instrument
Frequency sweep meter
Impedance instrument

Out Going Quality Control

Procedure: According to OQC inspection procedures NM - 2 - Q – 007
MIL-STD-105E II single sampling plan
Appearance: AQL = 0.4
Function: AQL = 0.04
Dimension: 20 PCS/lot , with the RE = 1, AC = 0 for inspection determination
ORT: 5 PCS/ lot, Lot define one model by weekly
Quality skill and statistical report
Pareto, Trend chart

Laboratory Experiment Flow Chart

Experiment Capability

Test ItemTesting condition
Life TestPink noise, White noise, IEC 268-5 2.83V 96H
Heat Test+ 60℃±2℃ 48 hours
Cold Test- 25℃±3℃ 48 hours
Humidity Test+ 40℃±2, Relative Humidity 90 - 95%, 48 hours
Temperature/ Humidity in Operating60℃ 30 minutes, Within 10 minutes , -40℃ 30 minutes, 5 times, In total 5.8H
Salt Spray TestSalt spray test for 24H, Fellow IEC - 68 - 11 - ka Standards
Drop TestThe speaker shall be dropped (A) times on iron as shown in the figure (A=6)
Packed Vibration TestAmplitude 1.5mm, Sine sweeping 3H with 30±15HZ, along X, Y, and Z axes
ISTA Packaging drop TestDrop one corner, three edges and six surfaces, Test height is 1m, Drop 6 times
End product drop TestTest height is 1m, Drop 6 times;
HSF compliance TestHSF compliance test with material, WIP, finished product and accessories.
RCA charged coating abrasion TestApplying 175g pressure with RCA tape back and forth 200 times.(According to customer standards)
Wire insertion force TestPlug the wire plug with the block for 100 times; insertion force and pull force according to the "wire plug force standard".
Wire tension TestThe wire core is fixed on the pull meter and the other end is fixed with wire Housing.
Thermal shock TestBegin with 25℃ and humidity 60%, Temperature   humidity requirements change with time according to "TH test profile". In total 53H
Electroplated layer abrasion TestWith three layers of clean cloth wrapped in the upper part of the 500g weight, dip in the purity of 99% alcohol, then scrub the Plating surface 100times, Each trip 25mm.
Pinhole testAccording to JIS C-3003-6. Inspection of copper wire.



2D Projector

3D Projector

Salt Spray Test


Life Test Instrument

Constant Temperature and Humidity Instrument

Extremely Hot Oven

Charged Coating Abrasion Test Instrument

Charged Coating Abrasion Test Instrument

Vibration Test Instrument

Drop Test Instrument

Wire Insertion Force Test Instrument

Pulsed Coil Tester

Pin Hole Test AC Power Supply

Quality System

ISO certificate